Antibacterial assay-guided isolation of active compounds from Artocarpus heterophyllus heartwoods

Abstract

Context: Preparations from Artocarpus heterophyllus Lam. (Moraceae) heartwoods are used in the traditional folk medicine for the treatment of inflammation, malarial fever, and to prevent bacterial and fungal infections.

Objective: The objective of this study was to isolate pure antibacterial compounds from A. heterophyllus heartwoods.

Materials and methods: The dried and powdered A. heterophyllus heartwoods were successively extracted with the following solvents: hexane, ethyl acetate, and methanol. Each of the extracts was screened for their antibacterial activities using a disc diffusion method (10?mg/disc). Their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined using a broth microdilution method. The extract that showed the strongest antibacterial activities was fractionated to isolate the active compounds by an antibacterial assay-guided isolation process.

Results and discussion: The ethyl acetate extract exhibited the strongest antibacterial activities against Streptococcus mutans, S. pyogenes, and Bacillus subtilis with MIC values of 78, 39, and 9.8?µg/mL, respectively. Based on an antibacterial assay-guided isolation, four antibacterial compounds: cycloartocarpin (1), artocarpin (2), artocarpanone (3), and cyanomaclurin (4) were purified. Among these isolated compounds, artocarpin exhibited the strongest antibacterial activity against Gram-positive bacteria, including S. mutans, S. pyogenes, B. subtilis, Staphylococcus aureus, and S. epidermidis with MICs of 4.4, 4.4, 17.8, 8.9, and 8.9?µM, respectively, and MBCs of 8.9, 8.9, 17.8, 8.9, and 8.9?µM, respectively, while artocarpanone showed the strongest activity against Escherichia coli, a Gram-negative bacteria with MIC and MBC values of 12.9 and 25.8?µM, respectively. Only artocarpin showed inhibitory activity against Pseudomonas aeruginosa with an MIC of 286.4?µM.     

Bioassay-guided isolation and evaluation of antimicrobial compounds from Ixora megalophylla against some oral pathogens

Context Ixora megalophylla Chamch. (Rubiaceae) is a new plant species recently found in southern Thailand. Ethyl acetate extracts of its leaves and stems showed antimicrobial activities.

Objectives To isolate and identify the antimicrobial compounds from I. megalophylla leaves and stems.

Materials and methods The dried leaves (1.7?kg) and stems (3.5?kg) were consecutively extracted with petroleum ether (5?L?×?4), ethyl acetate (5?L?×?3) and ethanol (5?L?×?4) under reflux conditions. The ethyl acetate extract was subjected to an antimicrobial assay guided isolation with Candida albicans and Streptococcus mutans. Compounds 1–10 were identified by ¹H NMR, ¹³C NMR and EI-MS. Minimal lethal concentration (MLC) against C. albicans and Streptococcus spp. was determined using a broth microdilution method for 48 and 24?h, respectively.

Results and discussion On the basis of the antimicrobial assay guided isolation, 10 known compounds, including vanillic acid (1), syringic acid (2), 4-hydroxy benzaldehyde (3), scopoletin (4), loliolide (5), syringaldehyde (6), sinapaldehyde (7), coniferaldehyde (8), syringaresinol (9) and 2,2′-dithiodipyridine (10), were identified. Compounds 1–5 were purified from the ethyl acetate extract of the leaves, while 6–9 and 10 were from the ethyl acetate and ethanol extracts of the stems, respectively. Among these isolates, 10 showed the strongest antibacterial activities against S. mutans and Streptococcus mitis, with minimum inhibitory concentrations (MICs) of 2–4?μg/mL, and MLC of 4?μg/mL, as well as having a weak antifungal activity against C. albicans (MIC of 125?μg/mL). This is the first report of the antimicrobial activities of 10.     

Anti-HIV-1 integrase compound from Pometia pinnata leaves

Abstract

Context: HIV-1 integrase (HIV-1 IN) is a key enzyme involved in the replication cycle of the retrovirus. Any new knowledge on inhibitors of this enzyme could provide essential clues for the development of anti-HIV drugs.

Objective: To evaluate anti-HIV-1 IN activity of some Thai medicinal plant extracts, and the extract that possessed the strongest anti-HIV-1 IN activity was subjected to isolation of the active compounds.

Materials and methods: Ethanol extracts of eight Thai medicinal plants were evaluated for their inhibitory effect against HIV-1 IN. An extract of Pometia pinnata J. R. Forst. & G. Forst (Sapindaceae) leaves that possessed the strongest anti-HIV-1 IN activity was fractionated to isolate the active compounds by anti-HIV-1 IN assay-guided isolation process.

Results and discussion: The leaf extract from P. pinnata had the strongest anti-HIV-1 IN activity with an IC₅₀ value of 8.8?µg/mL. An anti-HIV-1 IN assay-guided isolation of the active compounds from a leaf extract of P. pinnata resulted in the isolation of one active compound, identified as proanthocyanidin A2. Proanthocyanidin A2 showed satisfactory anti-HIV-1 IN activity with an IC₅₀ value of 30.1?µM. Three flavonoids, epicatechin, kaempferol-3-O-rhamnoside, quercetin-3-O-rhamnoside; a glycolipid, 1-O-palmitoyl-3-O-[α-.-galactopyranosyl-(1?→?6)-β-.-galactopyranosyl]-sn-glycerol; a steroidal glycoside; stigmasterol-3-O-glucoside; and a pentacyclic triterpenoid saponin, 3-O-α-.-arabinofuranosyl-(1?→?3)-[α-.-rhamnopyranosyl-(1?→?2)]-α-.-arabinopyranosyl hederagenin were also isolated but were inactive at a concentration of 100?µM.     

Anti-HIV-1 integrase activity and molecular docking of compounds from Albizia procera bark

Abstract

Context: Albizia procera (Roxb.) Benth. (Mimosaceae) has been traditionally used in Thai longevity preparations. Thus, searching for HIV-1 integrase (HIV-1 IN) agents from natural sources is of interest.

Objective: The objective of this study is to examine the inhibitory activity against HIV-1 IN of compounds isolated from the stem bark of Albizia procera.

Materials and methods: The EtOH extract and isolated compounds of Albizia procera bark were examined for anti-HIV-1 IN activity at various concentrations (10–100?µg/mL and 10–100?µM) using the multiplate integration assay and molecular docking.

Results and discussions: The results showed that the ethanol extract had good anti-HIV-1 IN activity with an IC₅₀ value of 19.5?µg/mL, whereas ethyl acetate fraction exhibited the most potent with an IC₅₀ value of 19.1?µg/mL, followed by water fraction (IC₅₀ value?=?21.3?µg/mL), hexane and chloroform fractions (IC₅₀ value?>?100?µg/mL), respectively. From bioassay-guided isolation, the ethyl acetate fraction was further separated to give two compounds which are (+)-catechin (1) and protocatechuic acid (2), respectively. Of the tested samples, (+)-catechin (1) exhibited appreciable activity against HIV-1 IN with an IC₅₀ value of 46.3?µM, whereas protocatechuic acid (2) showed mild activity with 46.0% inhibition at concentration of 100?µM. (+)-Catechin (1) could interact with Thr66, Gly148, and Glu152 in the core domain of IN enzyme, whereas protocatechuic acid (2) could bind with Thr66, His67, Glu152, Asn155, and Lys159. This is the first report on anti-HIV-1 IN activity of Albizia procera bark. These results may suggest that Albizia procera bark has potential as anti-HIV-1 IN agent.     

Bioassay-guided isolation of Poliovirus-inhibiting constituents from Zephyranthes candida

Abstract

Context: Plants of the Zephyranthes genus are globally used in folk medicine. In a previous study, Zephyranthes candida Linn. (Amaryllidaceae) was identified as having antiviral properties; this led to anti-poliovirus assay-guided isolation of compounds from crude methanol extract of the plant.

Objective: Isolation of anti-poliovirus constituents from Z. candida.

Material and methods: Active chloroform fraction from crude methanol extract of Z. candida (whole plant) was subjected to bioassay-guided fractionation; repeated column and preparative thin layer chromatography led to isolation of active compounds. Chemical structures were identified using spectroscopic techniques. Using serial two-fold dilution of maximum non-toxic concentration (MNTC) of each compound (0.0625–1?µg/mL for lycorine and 0.625–10?µg/mL for trisphaeridine and 7-hydroxy-3′,4′-methylenedioxyflavan), the ability of extracts to inhibit viral-induced cell death in tissue culture was evaluated 72?h post-infection by the colorimetric method using MTT (3-[4,5-dimethylthiazol–2-yl]-2,5-diphenyltetrazolium bromide) dye. Regression analysis was used to determine 50% inhibitory concentration (IC₅₀) and 50% cytotoxicity concentration (CC₅₀), from which selective index (SI) was calculated.

Results: From the chloroform fraction, three compounds were isolated and identified, namely lycorine (1), trisphaeridine (2), and 7-hydroxy-3′,4′-methylenedioxyflavan (3) as the anti-polioviral components. Lycorine was the most active, with an IC₅₀ value of 0.058?µg/mL followed by trisphaeridine (2) with an IC₅₀ of 0.1427?µg/mL, and 7-hydroxy-3′,4′-methylenedioxyflavan (3) with an IC₅₀ of 0.2384?µg/mL.

Discussions and conclusions: The antipoliovirus activity of trisphaeridine (2) and 7-hydroxy-3′,4′-methylenedioxyflavan (3) is established in this report; these compounds are of moderate toxicity and have very good SI. They could be a potential template for the development of a new antiviral agent.     

Antimicrobial,anticancer, and antioxidant compounds from Premna resinosa growing in Saudi Arabia

Context: Premna resinosa (Hochst.) Schauer (Lamiaceae) is used in many places to treat bronchitis, respiratory illness and convulsions of the rib cage.

Objective: This study evaluates the anticancer, antimicrobial and antioxidant activities of P. resinosa, and isolates some responsible constituents.

Materials and methods: The methanol extract of P. resinosa aerial parts and its fractions (n-hexane, dichloromethane, ethyl acetate and n-butanol) were tested. Antimicrobial activity was tested using microdilution method against three Gram-positive and four Gram-negative bacteria. The tested concentrations ranged from 4000 to 7.8?μg/mL and MIC values were determined after 24?h incubation. Anticancer activity was evaluated against three human cancer cell lines (Daoy, HepG2 and SK-MEL28) using MTT assay. Antioxidant activity was investigated by DPPH scavenging method and β-carotene-linoleic acid assay.

Results: The greatest antimicrobial activity was exhibited by n-hexane fraction (MIC 10?μg/mL) against Staphylococcus aureus, Enterococcus faecalis, and Shigella flexneri. The n-hexane fraction induced the greatest cytotoxic activity against Daoy, HepG2, and SK-MEL28 cell lines with IC₅₀ values of 9.0, 8.5 and 13.2, respectively. Moreover, the dichloromethane and ethyl acetate fractions showed the highest antioxidant potential. A bioassay-guided fractionation led to the isolation and characterization of seven compounds for the first time, namely, quercetin (1), 3-methoxy quercetin (2), kaempferol (3), 3-methoxy kaempferol (4), myricetin 3,7,3′-trimethyl ether (5), lupeol (6), and stigmasterol (7).

Conclusion: Our results indicate that P. resinosa is a source for antimicrobial and cytotoxic compounds. However, further work is required to isolate other active principles and to determine the mechanism of action.     

Compounds from Sedum caeruleum with antioxidant,anticholinesterase, and antibacterial activities

Context: This is the first study on the phytochemistry, antioxidant, anticholinesterase, and antibacterial activities of Sedum caeruleum L. (Crassulaceae).

Objective: The objective of this study is to isolate the secondary metabolites and determine the antioxidant, anticholinesterase, and antibacterial activities of S. caeruleum.

Materials and methods: Six compounds (1–6) were isolated from the extracts of S. caeruleum and elucidated using UV, 1D-, 2D-NMR, and MS techniques. Antioxidant activity was investigated using DPPH^?, CUPRAC, and ferrous-ions chelating assays. Anticholinesterase activity was determined against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes using the Ellman method. Antibacterial activity was performed according to disc diffusion and minimum inhibitory concentration (MIC) methods.

Results: Isolated compounds were elucidated as ursolic acid (1), daucosterol (2), β-sitosterol-3-O-β-d-galactopyranoside (3), apigenin (4), apigetrin (5), and apiin (6). The butanol extract exhibited highest antioxidant activity in all tests (IC₅₀ value: 28.35?±?1.22?µg/mL in DPPH assay, IC₅₀ value: 40.83?±?2.24?µg/L in metal chelating activity, and IC₅₀ value: 23.52?±?0.44?µg/L in CUPRAC), and the highest BChE inhibitory activity (IC₅₀ value: 36.89?±?0.15?µg/L). Moreover, the chloroform extract mildly inhibited (MIC value: 80?µg/mL) the growth of all the tested bacterial strains.

Discussion and conclusion: Ursolic acid (1), daucosterol (2), β-sitosterol-3-O-β-d-galactopyranoside (3), apigenin (4), apigetrin (5), and apiin (6) were isolated from Sedum caeruleum for the first time. In addition, a correlation was observed between antioxidant and anticholinesterase activities of bioactive ingredients of this plant.     

Flavonoids,cytotoxic, antioxidant and antibacterial activities of Evax pygmaea

Context: Phytochemical study and biological potential of Evax pygmaea (L.) Brot. (Asteraceae) are reported for the first time.

Objective: To identify the secondary metabolites of Evax pygmaea and to determine its antioxidant, antibacterial and cytotoxic activities.

Materials and methods: Dried aerial parts (1?kg) were macerated in 70% MeOH (5?L) during 72?h. The concentrated hydromethanolic extract was subjected to extractions with chloroform (3?×?300?mL), ethyl acetate (3?×?300?mL) and n-butanol (3?×?300?mL), successively. VLC of combined ethyl acetate (EAEP) and n-butanol (BEP) fractions was followed by column purifications. Antioxidant activity was investigated using DPPH, CUPRAC, and metal chelating, β-carotene/linoleic acid and ABTS assays. Agar method was used in the antibacterial study. Cytotoxic activity was determined by Brine shrimp lethality test in DMSO and ethanol, at varying concentrations (2, 1 and 0.2%) and (1, 0.2 and 0.1%) successively.

Results: Quercetin (1), isorhamnetin 3-O-β-d-xyloside (2), isorhamnetin 3-O-β-d-glucoside (3), quercetin 3-O-β-d-glucoside (4), quercetin 7-O-β-D-glucoside (5), patuletin 3-O-β-d-glucoside (6) were isolated from for the first time from Evax genus. The EAEP was the most active in ABTS (IC₅₀: <3.125?μg/mL) assay whereas the BEEP exhibited the highest activity in the β-carotene/linoleic acid assay (IC₅₀: <3.125?μg/mL). The EAEP and BEP exhibited good antibacterial activity (MIC: 40–80 µg/mL). The plant did not show any toxicity (LD₅₀>80 µg/mL).

Discussion and conclusions: Six flavonoids were isolated for the first time from Evax pygmaea which exhibited good antioxidant and antibacterial activities.     

Antimicrobial and antioxidant effects of phenolic constituents from Klainedoxa gabonensis

Bioassay-guided fractionation of the methanol extract of the stem bark of Klainedoxa gabonensis Pierre ex Engl. (Irvingiaceae) afforded 12 compounds, namely, ellagic acid (1), ellagic acid 3,3′-dimethylether (2), gallic acid (3), methyl gallate (4), lupeol (5), β-amyrin (7), erythrodiol (8), oleanolic acid (9), betulinic acid (6), hederagenin (10), bayogenin acid (11), and stigmasterol-3-O-β-d-glucopyranoside (12). Compounds 1-3 and 7-12 were isolated for the first time from this genus. The structures were established on the basis of 1D/2D NMR experiments and mass spectrometric data. Crude extract, fractions (A, B, C and D) and pure compounds were tested for their antimicrobial activity using paper disk agar diffusion assay. The test delivered a range of low to high activities for phenolic compounds 1-4, low or missing activities for terpenoid compounds 5-11, and impressive very high antibacterial/antifungal values for two fractions C and D probably due to synergistic effects of compounds. The broth microdilution assay revealed MICs of 15.4-115.1?μg/mL for phenolic compounds, MICs higher than 1?mg/mL for terpenoids and MICs of 4.5-30.3?μg/mL for fractions C and D. The determination of the radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay gave high antioxidant values for the methanol extract and fraction D (IC₅₀ 10.45 and 5.50?μg/mL) as well as for the phenolic compounds 1-4 (IC₅₀ 45.50-48.25?mM) compared to the standard 3-t-butyl-4-hydroxyanisole (BHA) (IC₅₀ 44.20?mM).     

Antimicrobial activity of natural products from the flora of Northern Ontario,Canada

Abstract

Context: The number of multidrug resistant (MDR) microorganisms is increasing and the antimicrobial resistance expressed by these pathogens is generating a rising global health crisis. In fact, there are only a few antimicrobial agents left that can be used against MDR bacteria and fungi.

Objective: In this study, the antimicrobial activities of selected natural products from the flora of Northern Ontario against selected microorganisms are reported.

Materials and methods: Plants were collected from Sault Ste. Marie, Ontario, Canada, and ethanol extracts were prepared using EtOH:H₂O (1:1, v/v). Fungal cultures used in this study were Candida albicans ATCC 10231 and Schizosaccharomyces octosporus. Bacterial cultures employed included Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Mycobacterium phlei ATCC 11758, and Streptococcus lactis ATCC 19435. The microplate resazurin assay was used to screen for antimicrobial activity.

Results: Extracts of four plant species Chimaphila umbellata L. (Pyrolaceae), Betula papyrifera Marshall (Betulaceae), Rhus typhina L. (Anacardiaceae), and Fraxinus pennsylvanica Marshall (Oleaceae), and six compounds (gallic acid, ethyl gallate, caffeic acid, sinapic acid, gentisic acid, and chlorogenic acid) demonstrated antibacterial or antifungal activities with MICs ranging from 62.5 to 1000?µg/mL, respectively, for a chemical fraction of an extract from Betula papyrifera against the bacterium S. aureus.

Discussion and conclusion: The present study has shown that certain plant extracts and select fractions and standard chemical compounds exhibit antimicrobial effects. Prince’s Pine, Chimaphila umbellate, White Birch, Betula papyrifera, Staghorn Sumac, Rhus typhina, and Green Ash, Fraxinus pennsylvanica were the principal extracts exhibiting notable antibacterial and/or antifungal activities; while gallic acid, ethyl gallate, and caffeic acid demonstrated antibacterial activities and sinapic acid, gentisic acid, and chlorogenic acid demonstrated antifungal activities.     

Aldose reductase and protein tyrosine phosphatase 1B inhibitory active compounds from Syzygium cumini seeds

Abstract

Context: Syzygium cumini (L.) Skeels (Myrtaceae), commonly known as jamun, is an Indian plant, traditionally well known for its medicinal properties including antidiabetic activity.

Objective: To isolate the antidiabetic compounds from Syzygium cumini seeds and evaluate their activity using aldose reductase (AR) and protein-tyrosine phosphatase 1B (PTP1B) inhibition assays.

Materials and methods: The dried seeds were extracted with methanol and partitioned with ethyl acetate, butanol, and water. The extracts were screened for antidiabetic activity at a concentration of 100?µg/mL using in vitro AR and PTP 1B inhibition assays.

Results and discussion: The highly enriched fractions obtained from broad ethyl acetate fraction yielded maslinic acid (1), 5-(hydroxymethyl) furfural (2), gallic acid (3), valoneic acid dilactone (4), rubuphenol (5), and ellagic acid (6). Structures were elucidated by ¹H-NMR and ¹³C-NMR. The initial ethyl acetate fraction showed AR inhibitory activity with the IC₅₀ value of 2.50?μg/mL and PTP1B enzyme inhibition with the IC₅₀ value of 26.36?μg/mL. Compounds 3, 4, 5, and 6 were found to inhibit AR with IC₅₀ values of 0.77, 0.075, 0.165, and 0.12?μg/mL while the compounds 4, 5, and 6 inhibited PTP1B with IC₅₀ values of 9.37, 28.14, and 25.96?μg/mL, respectively.

Conclusion: The results of this study demonstrate that the isolated constituents show promising in vitro antidiabetic activity and, therefore, can be candidates for in vivo biological screening using relevant models to ascertain their antidiabetic activity.     

Anti-HIV-1 integrase compounds from Dioscorea bulbifera and molecular docking study

Context Dioscorea bulbifera L. (Dioscoreaceae) has been used in a traditional Thai longevity medicine preparation. Isolation of inhibitors from natural products is a potential source for continuous development of new HIV-1 integrase (IN) inhibitors.

Objective The objective of this study is to isolate the compounds and evaluate their anti-HIV-1 IN activity, as well as to predict the potential interactions of the compounds with an IN.

Materials and methods The ethyl acetate and water fractions (1–100?μg/mL) of Dioscorea bulbifera bulbils were isolated and tested for their anti-HIV-1 IN activity using the multiplate integration assay (MIA). The interactions of the active compounds with IN were investigated using a molecular docking method.

Results and discussions The ethyl acetate and water fractions of Dioscorea bulbifera bulbils afforded seven compounds. Among these, allantoin (1), 2,4,3′,5′-tetrahydroxybibenzyl (2), and 5,7,4′-trihydroxy-2-styrylchromone (5) were isolated for the first time from this plant. Myricetin (4) exhibited the most potent activity with an IC₅₀ value of 3.15?μM, followed by 2,4,6,7-tetrahydroxy-9,10-dihydrophenanthrene (3, IC₅₀ value=?14.20?μM), quercetin-3-O-β-d-glucopyranoside (6, IC₅₀ value?=?19.39?μM) and quercetin-3-O-β-d-galactopyranoside (7, IC₅₀ value?=?21.80?μM). Potential interactions of the active compounds (3, 4, 6, and 7) with the IN active site were additionally investigated. Compound 4 showed the best binding affinity to IN and formed strong interactions with various amino acid residues. These compounds interacted with Asp64, Thr66, His67, Glu92, Asp116, Gln148, Glu152, Asn155, and Lys159, which are involved in both the 3′-processing and strand transfer reactions of IN. In particular, galloyl, catechol, and sugar moieties were successful inhibitors for HIV-1 IN.     

Chemical constituents from Sedum aizoon and their hemostatic activity

Context: Sedum aizoon L. (Crassulaceae) (SA) is widely used to treat various hemorrhages in folk medicine. However, its hemostatic constituents are not yet clear.

Objective: The chemical constituents of EtOAc fraction from SA and their hemostatic activity were investigated to provide a basis for the application in folk use.

Materials and methods: The chemical constituents were isolated from the aerial parts of SA by column chromatography and identified by IR, MS, and NMR, then tested for hemostatic activity using the capillary method and coagulation assays including blood clotting time in vivo, and prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT) in vitro at concentrations of 300.0, 100.0, and 30.0?µg/mL.

Results: Eleven compounds were identified as p-hydroxybenzoic acid (1), gallic acid (2), protocatechuic acid (3), vallinic acid (4), thymine (5), caffeic acid (6), 5,7-dihydroxy chromone (7), pyrogallol (8), quercetin (9), kaempferol (10), and luteolin (11). This is the first report of compounds 3–8 being isolated from this plant. Compounds 2 (300.0 and 100.0?µg/mL), 4 (100.0?µg/mL), and 11 (100.0 and 30.0?µg/mL) significantly reduced the clotting time (p?Discussion and conclusion: SA produced hemostatic activity possibly related to the presence of gallic acid, vallinic acid, and luteolin, which may be potent candidates of hemostatic drug.     

Antibacterial activities of chemical constituents from the aerial parts of Hedyotis pilulifera

Context: Hedyotis pilulifera (Pit.) T.N. Ninh (Rubiaceae) has been used in Vietnamese ethnomedicine; the methanol extract exhibited antibacterial activity in our preliminary screening.

Objectives: In this study, compounds from H. pilulifera were isolated and their antibacterial activity in vitro was evaluated.

Materials and methods: The aerial parts of H. pilulifera (1.4?kg) were extracted with MeOH, suspended in water and ethyl acetate extract was chromatographed on a silica gel column. The structures of isolated compounds were elucidated by the combination analyses of spectroscopy including 1D-, 2D-NMR, HRMS and in comparison with the reported NMR data in the literature. All isolated compounds were evaluated for inhibitory effect using the microdilution method toward Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis, and MIC values were determined.

Results: Twenty compounds were isolated, including five triterpenoids, two steroids, two aromatic compounds, three fatty acids, one quinone derivative, one lignan glycoside, one ceramide and five glycolipids. Among these, oleanolic acid showed significant antibacterial activity against M. smegmatis with the MIC value of 2.5?μg/mL. Remarkably, rotungenic acid showed strong activity against S. aureus, B. subtilis, M. smegmatis with MIC values of 2.5, 2.5 and 1.25?μg/mL, respectively. Rotundic acid exhibited significant antibacterial activity against B. subtilis with the MIC value of 5?μg/mL. To the best of our knowledge, the antibacterial activity of rotungenic acid, stigmast-4-ene-3,6-dione and (2S,3S,4R,2′R)-2-(2′-hydroxytetracosanoylamino) octadecane-1,3,4-triol was reported for the first time.

Conclusions: Oleanolic acid, rotungenic acid, and rotundic acid were considered to be useful for developing new antimicrobial therapeutic agents for human.     

Chemical constituents and biological activities of Albizia myriophylla wood

Context: Albizia myriophylla Benth (Leguminosae) is a medicinal plant widely used in Thailand and other Asian countries as a folk medicine remedy for many ailments.

Objective: The objective of this study is to investigate the chemical compositions, antibacterial activity, and cytotoxicity of A. myriophylla wood.

Materials and methods: The structure identification of the isolated compounds was established using spectroscopic methods. In vitro antibacterial activity against Streptococcus mutans, Staphylococcus aureus, and Bacillus cereus and the cytotoxicity against KB cells of extracts and compounds from A. myriophylla were performed using broth microdilution and resazurin microplate assays, respectively. The lupinifolin content in A. myriophylla extracts was quantified by high-performance liquid chromatography.

Results: A rare flavan-3,4-diol (1) together with eight known compounds (2–9) were isolated from the wood of A. myriophylla. Compounds 4–9 exhibited anti-S. mutans activity, of which lupinifolin (5) was the most potent with an MIC value of 0.98?µg/mL, followed by its dihydroxy derivative 4 with an MIC value of 62.5?µg/mL. Compounds 4 and 5 also displayed marked antibacterial activity against B. cereus and S. aureus (MIC value 15.63–125?µg/mL) and showed strong cytotoxic activity against KB cells (IC₅₀ value 4.95–12.55?µg/mL). The lupinifolin contents in ethanol extracts from two different collections of this plant originating from central and southern Thailand were 93.85 and 0.04?mg/g, respectively.

Conclusion: This is the first report of compounds 1–4 from A. myriophylla. Compounds 4 and 5 showed potent antibacterial and cytotoxic activities compared with other isolates. The anti-S. mutans activity of A. myriophylla extracts seems to be related to the lupinifolin content.     

Antibacterial activity of Thai herbal extracts on acne involved microorganism

Ethyl acetate and methanol extracts of 18 Thai medicinal plants were investigated for their antibacterial activity against Propionibacterium acnes, Stapylococcus aureus, and S. epidermidis. Thirteen plant extracts were capable of inhibiting the growth of P. acnes and S. epidermidis, while 14 plant extracts exhibited an inhibitory effect on S. aureus. Based on the broth dilution method, the ethyl acetate extract of Alpinia galanga (L.) Wild. (Zingiberaceae) rhizome showed the strongest antibacterial effect against P. acnes, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 156.0 and 312.0 µg/mL, respectively. On the basis of bioassay-guided purification, the ethyl acetate extract was isolated to afford the antibacterial active compound, which was identified as 1′-acetoxychavicol acetate (1′-ACA). 1′-ACA had a strong inhibitory effect on P. acnes with MIC and MBC values of 62.0 and 250.0 µg/mL, respectively. Thus, 1′-ACA was used as an indicative marker for standardization of A. galanga extract using high performance liquid chromatography. These results suggest that A. galanga extract could be an interesting agent for further studies on an alternative treatment of acne.     

Xanthine oxidase/tyrosinase inhibiting,antioxidant, and antifungal oxindole alkaloids from Isatis costata

Phytochemical investigations on the ethyl acetate soluble fraction of the whole plant of Isatis costata Linn. (Brassicaseae) led to the isolation of the oxindole alkaloids costinones A (1), B (2), isatinones A (3), B (4), indirubin (5), and trisindoline (6). Compounds 1–6 displayed significant to moderate inhibition against xanthine oxidase enzyme with IC₅₀ values ranging from 90.3?±?0.06 to 179.6?±?0.04 µM, whereas the standard inhibitor of xanthine oxidase (allopurinol) had an IC₅₀ value of 7.4?±?0.07 µM. Compounds 1 (IC₅₀ 7.21?±?0.05 µM), 2 (IC₅₀ 9.40?±?0.03 µM), 3 (IC₅₀ 11.51?±?0.07 µM), 4 (IC₅₀ 12.53?±?0.06 µM), 5 (IC₅₀ 14.29?±?0.09 µM), and 6 (IC₅₀ 17.34?±?0.04 µM) exhibited pronounced activities when compared with the standard tyrosinase inhibitor l-mimosine (IC₅₀ 3.70?±?0.03 µM), along with DPPH radical scavenging activity with IC₅₀ 226, 270, 300, 320, 401, and 431 µM, respectively. The crude extract and compounds 1, 2, 5, and 6 showed significant antifungal activity against Trichophyton schoen leinii, Aspergillus niger, Candida albicans, Trichophyton simii, and Macrophomina phaseolina.     

Anti-Streptococcus mutans efficacy of Thai herbal formula used as a remedy for dental caries

Context: Traditional knowledge of herbal remedies plays an important role in the search for more effective alternative treatment of a variety of disorders. The ethnobotanical surveys in southern Thailand have revealed that 35 Thai herbal formulas have been used by Thai traditional healers against dental caries. However, the scientific evaluation to confirm their rational uses is scarce.

Objective: To test in vitro anti-Streptococcus mutans activity of Thai herbal formulas used against dental caries (THF-DC).

Materials and methods: Ethanol extracts of Thai herbal formulas were evaluated for antibacterial activity against S. mutans. Agar disc diffusion was employed as a preliminary screening assay, followed by broth microdilution assay to assess minimum inhibitory concentration (MIC). Furthermore, medicinal plants contained in the most active THF-DC were investigated for their phytochemicals.

Results: Eleven THF-DC extracts exhibited clear inhibition zones of 7.0–22.5?mm against S. mutans. Subsequent determination of their MIC revealed that the formula containing Albizia myriophylla Benth. (Leguminosae), Alpinia galanga (L.) Willd. (Zingiberaceae), Avicennia marina (Forssk.) Vierh. (Acanthaceae), and Ocimum sanctum L. (Lamiaceae) was the most active, with MIC at 250 µg/mL. Among these medicinal plants, A. myriophylla gave the strongest activity with MIC at 3.9 µg/mL, followed by A. marina with MIC at 62.5 µg/mL. Various classes of bioactive phytochemicals including tannins, flavonoids, alkaloids, and terpenoids were found in these extracts.

Conclusion: Anti-S. mutans activity of THF-DC extracts was established. Further investigations may be required for the isolation and chemical characterization of the active ingredients in A. myriophylla.     

In Vitro Antibacterial and Antifungal Activities of Extracts and Compounds from Uvaria scheffleri

Petroleum ether, dichloromethane, and ethanolic extracts of the stem bark and leaves of Uvaria scheffleri Diels (Annonaceae) exhibited antifungal activity against Aspergillus niger (wild strain), Aspergillus fumigatus (wild strain), and a Penicillium species (wild strain). The ethanol extract of the stem bark was also active against Candida albicans (Strain H6392). The dichloromethane extract of the leaves showed the highest antifungal activity and in addition it showed antibacterial activity against Staphylococcus aureus (NCTC 6571). Fractionation of the dichloromethane extract of the leaves yielded nine known compounds. They included a 1 : 1 mixture of stigmasterol (1) and β-sitosterol (2), which showed antifungal activity against Candida albicans. Others were 3-farnesylindole (3), 2′,6′-dihydroxy-3′,4′-dimethoxy-chalcone (4), 2′-hydroxy-3′,4′,6′-trimethoxychalcone (5), 5-hydroxy-7,8-dimethoxyflavanone (6), 5,7,8-trimethoxyflavanone (7), and a 3 : 2 mixture of 2′,6′-dihydroxy-4′-methoxychalcone (8) and 5,7-dihydroxyflavone (9). Compound 7 and the mixture of compounds 8 and 9 showed antibacterial activity against Escherichia coli (NCTC 10418, MIC 125 µg/ml) and Staphylococcus aureus (MIC 125 µg/ml), respectively. The mixture of compounds 8 and 9 was also active against Candida albicans (MIC 31.25 µg/ml), Aspergillus niger, Aspergillus fumigatus, and the Penicillium species (MIC 1000 µg/ml). We conclude that Uvaria scheffleri extracts contain compounds with antifungal and antibacterial activity. The activities observed in this study are weak. Based on previous studies, it is being speculated that, possibly, the most active compounds were lost during fractionation. Further work to isolate more antifungal and antibacterial compounds is suggested.