Biosynthesis of Chenodeoxycholic Acid in Man: STEREOSPECIFIC SIDE-CHAIN HYDROXYLATIONS OF 5β-CHOLESTANE-3α, 7α-DIOL

Stereospecific side-chain hydroxylations of 5β-cholestane-3α, 7α-diol were studied in mitochondrial and microsomal fractions of human liver. Incubation of 5β-cholestane-3α, 7α-diol resulted in hydroxylations at C-12, C-24, C-25, and C-26. Hydroxylations at C-24 and C-26 were accompanied by the introduction of additional asymmetric carbon atoms at C-24 and C-25 respectively, that led to the formation of two distinct pairs of diastereoisomers, namely 5β-cholestane-3α, 7α,24-triols (24R and 24S) and 5β-cholestane-3α, 7α,26-triols (25R and 25S). A sensitive and reproducible radioactive assay to measure the formation of the different biosynthetic 5β-cholestanetriols was developed. Optimal assay conditions for human mitochondrial and microsomal systems were tentatively established.     

Cholestenoic acids regulate motor neuron survival via liver X receptors

Cholestenoic acids are formed as intermediates in metabolism of cholesterol to bile acids, and the biosynthetic enzymes that generate cholestenoic acids are expressed in the mammalian CNS. Here, we evaluated the cholestenoic acid profile of mammalian cerebrospinal fluid (CSF) and determined that specific cholestenoic acids activate the liver X receptors (LXRs), enhance islet-1 expression in zebrafish, and increase the number of oculomotor neurons in the developing mouse in vitro and in vivo. While 3β,7α-dihydroxycholest-5-en-26-oic acid (3β,7α-diHCA) promoted motor neuron survival in an LXR-dependent manner, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (3βH,7O-CA) promoted maturation of precursors into islet-1⁺ cells. Unlike 3β,7α-diHCA and 3βH,7O-CA, 3β-hydroxycholest-5-en-26-oic acid (3β-HCA) caused motor neuron cell loss in mice. Mutations in CYP7B1 or CYP27A1, which encode enzymes involved in cholestenoic acid metabolism, result in different neurological diseases, hereditary spastic paresis type 5 (SPG5) and cerebrotendinous xanthomatosis (CTX), respectively. SPG5 is characterized by spastic paresis, and similar symptoms may occur in CTX. Analysis of CSF and plasma from patients with SPG5 revealed an excess of the toxic LXR ligand, 3β-HCA, while patients with CTX and SPG5 exhibited low levels of the survival-promoting LXR ligand 3β,7α-diHCA. Moreover, 3β,7α-diHCA prevented the loss of motor neurons induced by 3β-HCA in the developing mouse midbrain in vivo.Our results indicate that specific cholestenoic acids selectively work on motor neurons, via LXR, to regulate the balance between survival and death.     

Metabolism of Mono-and Dihydroxylated Bile Acids in Preparations of Human Liver

Abstract. The metabolism of tritium-labelled taurodeoxycholic acid, taurochenodeoxycholic acid, taurolithocholic acid and of [24-¹⁴C] lithocholic acid and [24-¹⁴C] 3-keto-5β-cholanoic acid was studied in fractions of human liver homogenates.—In the presence of microsomal fraction fortified with an NADPH-generating system a small conversion of taurodeoxycholic acid into taurocholic acid occurred. No significant hydroxylation of taurochenodeoxycholic acid, taurolithocholic acid or free lithocholic acid could be detected. In the presence of microsomal fraction fortified with NAD lithocholic acid was converted into 3-keto-5β-cholanoic acid. In the presence of microsomal fraction fortified with NADH, 3-keto-5β-cholanoic acid was reduced to isolithocholic acid and lithocholic acid (ratio 3:1). In the presence of 100000 × g supernatant fraction only lithocholic acid was formed from 3-keto-5β-cholanoic acid.—The physiological significance of the ability of human liver to convert lithocholic acid into isolithocholic acid is discussed.     

Cholic Acid Biosynthesis: THE ENZYMATIC DEFECT IN CEREBROTENDINOUS XANTHOMATOSIS

Cholic acid biosynthesis is defective in individuals with cerebrotendinous xanthomatosis (CTX) and is associated with the excretion of 5β-cholestane-3α,7α, 12α,25-tetrol, an intermediate in the 25-hydroxylation pathway of cholic acid in CTX. To define the enzymatic defect in CTX, two suspected precursors of cholic acid, namely 5β-[7β-³H]cholestane-3α,7α, 12α-triol and 5β-[24-¹⁴C]cholestane-3α,7α, 12α,24S,25-pentol were examined by both in vivo and in vitro experiments. A third precursor, 5β-[7β-³H]-cholestane-3α,7α, 12α,25-tetrol, was compared with them in vitro.     

Microbial transformation of mestanolone by Macrophomina phaseolina and Cunninghamella blakesleeana and anticancer activities of the transformed products

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. The structures of these metabolites were characterized as 17β-hydroxy-17α-methyl-5α-androsta-1-ene-3,11-dione (2), 14α,17β-dihydroxy-17α-methyl-5α-androstan-3,11-dione (3), 17β-hydroxy-17α-methyl-5α-androstan-1,14-diene-3,11-dione (4), 17β-hydroxy-17α-methyl-5α-androstan-3,11-dione (5), 11β,17β-dihydroxy-17α-methyl-5α-androstan-1-ene-3-one (6), 9α,11β,17β-trihydroxy-17α-methyl-5α-androstan-3-one (7), and 1β,11α,17β-trihydroxy-17α-methyl-5α-androstan-3-one (8). All the metabolites, except 5 and 6, were identified as new compounds. Substrate 1 (IC₅₀ = 27.6 ± 1.1 μM), and its metabolites 2 (IC₅₀ = 19.2 ± 2.9 μM) and 6 (IC₅₀ = 12.8 ± 0.6 μM) exhibited moderate cytotoxicity against the HeLa cancer cell line (human cervical carcinoma). All metabolites were noncytotoxic to 3T3 (mouse fibroblast) and H460 (human lung carcinoma) cell lines. The metabolites were also evaluated for immunomodulatory activity, and all were found to be inactive.

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. Some of them have exhibited moderate cytotoxicity against HeLa cancer cell line.     

Production and Property of Beta-Lactamases in Streptomyces: Comparison of the Strains Isolated Newly and Thirty Years Ago

Productivity and property of β-lactamases of Streptomyces strains isolated from soil some 30 years ago were studied in comparison with those of the newly isolated strains. At least three-quarters of the Streptomyces strains produced β-lactamase constitutively and extracellularly, mainly as penicillinases, as in the cases of those from the newly isolated strains. Strains such as S. albus, S. diastatochromogenes, S. fradiae, and S. lavendulae were the highest producing strains, and the amounts of β-lactamase activity they produced were comparable to those produced by Bacillus cereus 569/H and B. licheniformis 749/C. In isoelectric focusing, most strains contained one main β-lactamase band with a number of satellite bands, but some strains contained one band only. Although β-lactamases from most strains showed isoelectric points of pH 5 to 6, some strains produced β-lactamases with strongly basic isoelectric points of pH 8 to 9. Molecular weights were between 20,000 and 30,000. From these results, it is suggested that the proportion of the producing strains of Streptomyces and the properties of the β-lactamases have not been affected significantly by the introduction of penicillin into the natural environment, in contrast to the cases of other microorganisms.     

Diastereoselective approach to rationally design tetrahydro-β-carboline–isatin conjugates as potential SERMs against breast cancer

A series of tetrahydro-β-carboline–isatin conjugates, with varying substituents as well as stereochemistry at C-1 and C-5 position of tetrahydro-β-carboline (THβC) and isatin ring, were prepared and assayed for anti-proliferative efficacy on Estrogen Responsive ER(+) (MCF-7) and ER(−ve) MDA-MB-231 cell-lines. The synthesized scaffolds displayed selective anti-proliferative efficacy against MCF-7 cell-line with the most active conjugate 8b exhibiting an IC₅₀ value of 37.42 μM, comparable to that of peganumine A, a tetrahydro-β-carboline analogue, isolated from Peganum harmala. The synthesized compound 8b was also more potent than the standard drug tamoxifen (IC₅₀ = 50 μM against MCF-7). The observed activities were further corroborated via docking studies in ER-α (PDB ID: 3ERT).

A series of tetrahydro-β-carboline–isatin conjugates was prepared and assayed for anti-proliferative activities on Estrogen Responsive ER(+) and non-responsive ER(−ve) cell-lines.     

Structural modification of olibergin A,an isoflavonoid,from Dalbergia stipulacea Roxb. and its cytotoxicity

Fifteen derivatives were synthesized from olibergin A, a major isoflavonoid isolated from the stems of Dalbergia stipulacea Roxb. All compounds were evaluated for cytotoxicity against HCT-116, HT-29, MCF-7 and vero cell lines using MTT assay. Cytotoxicity results showed 5-hydroxy-7,2′,4′,5′-tetramethoxyisoflavone (5) was the most active with IC₅₀ values of 19.03 ± 0.70, 10.83 ± 1.65, 12.53 ± 0.70 and 13.53 ± 0.84 μM against HCT-116, HT-29, MCF-7 and vero cell lines, respectively. It should be noted that 5-hydroxy-7,2′,4′,5′-tetramethoxyisoflavone (5) showed two times less toxicity against vero cells than the cisplatin standard (IC₅₀ = 6.55 ± 0.81 μM) while 5 and cisplatin exhibited nearly equal cytotoxicity against the MCF-7 cell line. 5,7,2′,4′,5′-Pentamethoxyisoflavanone (10) showed an IC₅₀ value of 30.34 ± 1.15 μM against the HCT-116 cell line and exhibited weak cytotoxicity against normal cells, the vero cell line. In addition, 5,7,4′-trihydroxy-2′,5′-dimethoxyisoflavan oxime (13) demonstrated cytotoxicity against HT-29 cells with an IC₅₀ value of 31.41 ± 1.38 μM and displayed weak activity toward the vero cell line. The information revealed that these compounds were suitable for development to anticancer agents against HCT-116, HT-29 and MCF-7 cell lines.

Fifteen derivatives were synthesized from olibergin A, a major isoflavonoid isolated from the stems of Dalbergia stipulacea Roxb.     

Glycosylation of luteolin in hydrophilic organic solvents and structure–antioxidant relationships of luteolin glycosides

An effective approach was developed to biotransform luteolin glycosides in hydrophilic organic solvents. Bacillus cereus A46 cells showed high activity and stability in 5–20% (v/v) DMSO with 90–98% conversion rates of luteolin glycosides. Five glycosides of luteolin 7-O-β-glucoside, luteolin 4′-O-β-glucoside, luteolin 3′-O-β-glucoside, luteolin 7,3′-di-O-β-glucoside and luteolin 7,4′-di-O-β-glucoside were obtained. The addition of DMSO greatly promoted the solubility of luteolin and further regulated the formation of the main products from five luteolin glycosides to luteolin 7-O-β-glucoside (931.2 μM). Fourteen flavonoids and anthraquinones were used as tentative substrates. Glycosylation positions were located at the C-7, C-3′ or C4′ hydroxyl groups of flavonoids and C-5 hydroxyl group of anthraquinones. The 3′,4′-dihydroxy arrangement played the key role for the antioxidant activity of luteolin.

Efficient glycosylation of luteolin in organic solvents and the structure–antioxidant relationships of luteolin glycosides were reported for the first time.     

Relationship Between Polyene Resistance and Sterol Compositions in Cryptococcus Neoformans

Six mutants of Cryptococcus neoformans resistant to nystatin and pimaricin and three mutants resistant to amphotericin B were isolated by ultraviolet irradiation techniques from two wild-type strains. The major sterols of the wild-type strains were Δ⁷-ergosten-3β-ol and ergosterol. All six mutants resistant to nystatin and pimaricin showed either loss of ergosterol and concurrent production of Δ^{7, 22}-ergostadien-3β-ol and Δ⁷-ergosten-3β-ol, or loss of both the wild-type sterols, with production of Δ⁸⁽⁹⁾-ergosten-3β-ol and Δ^{5, 8(9), 22}-ergostatrien-3β-ol. The mutants producing Δ^{7, 22}-ergostadien-3β-ol and Δ⁷-ergosten-3β-ol showed relatively low levels of resistance to nystatin and pimaricin, whereas the mutants producing Δ⁸⁽⁹⁾-ergosten-3β-ol and Δ^{5, 8(0), 22}-ergostatrien-3β-ol showed a high level of resistance to either drug. Although highly resistant to amphotericin B, however, the three mutants produced sterol compositions identical to those of the wild types, indicating that the strains acquired resistance other than by alteration of the membrane sterols. The mutants producing Δ⁸⁽⁹⁾ and Δ^{5, 8(9), 22} sterols were not virulent for mice, showed reduced growth rates at 25 C, and failed to grow at 37 C. The other mutants showed a slightly reduced rate of growth both at 25 and 37 C, and the virulence in mice was slightly reduced in comparison with that of the wild types. These comparisons were on gross observations and were not statistically analyzed.     

Structural transformation of methasterone with Cunninghamella blakesleeana and Macrophomina phaseolina

An anabolic-androgenic synthetic steroidal drug, methasterone (1) was transformed by two fungi, Cunninghamella blakesleeana and Macrophimina phaseclina. A total of six transformed products, 6β,7β,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (2), 6β,7α,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (3), 6α,17β-dihydroxy-2α,17α-dimethyl-5α-androstane-3,7-dione (4), 3β,6β,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-7-one (5), 7α,17β-dihydroxy-2α,17α-dimethyl-5α-androstane-3-one (6), and 6β,9α,17β-trihydroxy-2α,17α-dimethyl-5α-androstane-3-one (7) were synthesized. Among those, compounds 2–5, and 7 were identified as new transformed products. MS, NMR, and other spectroscopic techniques were performed for the characterization of all compounds. Substrate 1 (IC₅₀ = 23.9 ± 0.2 μg mL⁻¹) showed a remarkable anti-inflammatory activity against nitric oxide (NO) production, in comparison to standard LNMMA (IC₅₀ = 24.2 ± 0.8 μg mL⁻¹). Whereas, its metabolites 2, and 7 showed moderate inhibition with IC₅₀ values of 38.1 ± 0.5 μg mL⁻¹, and 40.2 ± 3.3 μg mL⁻¹, respectively. Moreover, substrate 1 was found to be cytotoxic for the human normal cell line (BJ) with an IC₅₀ of 8.01 ± 0.52 μg mL⁻¹, while metabolites 2–7 were identified as non-cytotoxic. Compounds 1–7 showed no cytotoxicity against MCF-7 (breast cancer), NCI-H460 (lung cancer), and HeLa (cervical cancer) cell lines.

Fungal transformation of methasterone resulted in six products (2–7). 2–5, and 7 were identified as new. Substrate 1 showed remarkable anti-inflammatory activity but was cytotoxic. Products 2 and 7 showed moderate activity but were non-cytotoxic.     

Newly synthesised oxime and lactone derivatives from Dipterocarpus alatus dipterocarpol as anti-diabetic inhibitors: experimental bioassay-based evidence and theoretical computation-based prediction

Dipterocarpus alatus-derived products are expected to exhibit anti-diabetes properties. Natural dipterocarpol (1) was isolated from Dipterocarpus alatus collected in Quang Nam province, Vietnam; afterwards, 20 derivatives including 13 oxime esters (2 and 3a–3m) and 7 lactones (4, 5, 6a–6e) were semi-synthesised. Their inhibitory effects towards diabetes-related proteins were investigated experimentally (α-glucosidase) and computationally (3W37, 3AJ7, and PTP1B). Except for compound 2, the other 19 compounds (3a–3m, 4, 5, and 6a–6d) are reported for the first time, which were modified at positions C-3, C-24 and C-25 of the dipterocarpol via imidation, esterification, oxidative cleavage and lactonisation reactions. A framework based on docking-QSARIS combination was proposed to predict the inhibitory behaviour of the ligand-protein complexes. Enzyme assays revealed the most effective α-glucosidase inhibitors, which follow the order 5 (IC₅₀ of 2.73 ± 0.05 μM) > 6c (IC₅₀ of 4.62 ± 0.12 μM) > 6e (IC₅₀ of 7.31 ± 0.11 μM), and the computation-based analysis confirmed this, i.e., 5 (mass: 416.2 amu; polarisability: 52.4 ų; DS: −14.9 kcal mol⁻¹) > 6c (mass: 490.1 amu; polarisability: 48.8 ų; DS: −13.7 kcal mol⁻¹) > 6e (mass: 549.2 amu; polarisability: 51.6 ų; DS: −15.2 kcal mol⁻¹). Further theoretical justifications predicted 5 and 6c as versatile anti-diabetic inhibitors. The experimental results encourage next stages for the development of anti-diabetic drugs and the computational strategy invites more relevant work for validation.

Dipterocarpus alatus-derived products are expected to exhibit anti-diabetes properties.     

αdβ2 Integrin Is Expressed on Human Eosinophils and Functions as an Alternative Ligand for Vascular Cell Adhesion Molecule 1 (VCAM-1)

The β2 family of integrins, CD11a, CD11b, CD11c, and αd, are expressed on most leukocytes. We show that the newest member of this family, αd, is expressed on human eosinophils in peripheral blood, and surface expression can be upregulated within minutes by phorbol ester or calcium ionophore A23187. Culture of eosinophils with interleukin 5 (IL-5) leads to a two- to fourfold increase in αd levels by 3–7 d without a change in α4 integrin expression. Eosinophils isolated from late phase bronchoalveolar lavage fluids express αd at levels similar to that seen after 3 d of IL-5 culture. Regarding αdβ2 ligands, in both freshly isolated and IL-5–cultured eosinophils, as well as αdβ2-transfected Chinese hamster ovary cells, αdβ2 can function as a ligand for vascular cell adhesion molecule 1 (VCAM-1). This conclusion is based on the ability of monoclonal antibodies to αd, β2, or VCAM-1 to block cell attachment in static adhesion assays. In experiments with eosinophils, the relative contribution of αdβ2 integrin– mediated adhesion is enhanced after IL-5 culture. These experiments demonstrate that αdβ2 is an alternative ligand for VCAM-1, and this integrin may play a role in eosinophil adhesion to VCAM-1 in states of chronic inflammation.     

Genotypic versus phenotypic characterization, with respect to beta-lactam susceptibility, of Haemophilus influenzae isolates exhibiting decreased susceptibility to beta-lactam resistance markers

Among 165 Spanish Haemophilus influenzae isolates with mutations in the ftsI gene (ftsI⁺) (2005 to 2007), 73% were β-lactamase negative and 26.7% were positive. The proportion of β-lactamase-negative isolates to β-lactamase-positive isolates was 2:1 to 4:1 in general, versus 1:3 in pediatric hospitals. Among 44 β-lactamase-positive strains, 8 strains produced ROB-1 (5 from the pediatric hospital). β-Lactamase-positive ftsI⁺ strains were phylogenetically closer than were β-lactamase-negative strains.     

Moxalactam (6059-S), a novel 1-oxa-beta-lactam with an expanded antibacterial spectrum: laboratory evaluation

Moxalactam (6059-S) {7β-[2-carboxy-2-(4-hydroxyphenyl)acetamido]-7α-methoxy-3-[[(1-methyl-1H-tetrazol-5-yl)thio]-methyl]-1-oxa-1-dethia-3-cephem-4- carboxylic acid disodium salt} is a new semisynthetic 1-oxa-β-lactam derivative for parenteral use. It was highly active against a broad range of gram-negative microorganisms, including those resistant to other cephalosporins. Moreover, it had widely expanded antibacterial spectra which included Haemophilus influenzae, indole-positive Proteus, Enterobacter, Serratia marcescens, Pseudomonas aeruginosa, and Bacteroides fragilis. When a large number of clinical isolates of the above-named bacilli were tested by the agar dilution method, using an inoculum size of one loopful of 10⁶ or 10⁸ organisms or both per ml, the 70% minimal inhibitory concentrations at the lower inoculum were 0.2, 0.2, 0.4, 0.8, 25, and 0.8 μg/ml, respectively. Its activity appeared to be independent of inoculum size and addition of serum. In these organisms, morphological response of the exposed cells revealed that the bacteriolytic effect of 6059-S was initiated by a concentration equivalent to the minimal inhibitory concentration. 6059-S was markedly bactericidal to both β-lactamase-producing and -nonproducing strains of Escherichia coli; this was well reflected by its extraordinary stability to microbial β-lactamase degradation. Administered subcutaneously in mice, 6059-S attained plasma levels and a half-life similar to those of cefazolin and exhibited potent protective efficacy against systemic infections; it also proved to be significantly more effective than either sulbenicillin or piperacillin against Pseudomonas aeruginosa and than either cefazolin or cefmetazole against a variety of other gram-negative bacteria.     

Boronic Acid Transition State Inhibitors Active against KPC and Other Class A β-Lactamases: Structure-Activity Relationships as a Guide to Inhibitor Design

Boronic acid transition state inhibitors (BATSIs) are competitive, reversible β-lactamase inhibitors (BLIs). In this study, a series of BATSIs with selectively modified regions (R1, R2, and amide group) were strategically designed and tested against representative class A β-lactamases of Klebsiella pneumoniae, KPC-2 and SHV-1. Firstly, the R1 group of compounds 1a to 1c and 2a to 2e mimicked the side chain of cephalothin, whereas for compounds 3a to 3c, 4a, and 4b, the thiophene ring was replaced by a phenyl, typical of benzylpenicillin. Secondly, variations in the R2 groups which included substituted aryl side chains (compounds 1a, 1b, 1c, 3a, 3b, and 3c) and triazole groups (compounds 2a to 2e) were chosen to mimic the thiazolidine and dihydrothiazine ring of penicillins and cephalosporins, respectively. Thirdly, the amide backbone of the BATSI, which corresponds to the amide at C-6 or C-7 of β-lactams, was also changed to the following bioisosteric groups: urea (compound 3b), thiourea (compound 3c), and sulfonamide (compounds 4a and 4b). Among the compounds that inhibited KPC-2 and SHV-1 β-lactamases, nine possessed 50% inhibitory concentrations (IC₅₀s) of ≤600 nM. The most active compounds contained the thiopheneacetyl group at R1 and for the chiral BATSIs, a carboxy- or hydroxy-substituted aryl group at R2. The most active sulfonamido derivative, compound 4b, lacked an R2 group. Compound 2b ({"type":"entrez-protein","attrs":{"text":"S02030","term_id":"83679","term_text":"pir||S02030"}}S02030) was the most active, with acylation rates (k₂/K) of 1.2 ± 0.2 × 10⁴ M⁻¹ s⁻¹ for KPC-2 and 4.7 ± 0.6 × 10³ M⁻¹ s⁻¹ for SHV-1, and demonstrated antimicrobial activity against Escherichia coli DH10B carrying bla_SHV variants and bla_KPC-2 or bla_KPC-3 and against clinical strains of Klebsiella pneumoniae and E. coli producing different class A β-lactamase genes. At most, MICs decreased from 16 to 0.5 mg/liter.     

In vitro and in silico studies of SARS-CoV-2 main protease Mpro inhibitors isolated from Helichrysum bracteatum

Discovering SARS-CoV-2 inhibitors from natural sources is still a target that has captured the interest of many researchers. In this study, the compounds (1–18) present in the methanolic extract of Helichrysum bracteatum were isolated, identified, and their in vitro inhibitory activities against SARS-CoV-2 main protease (M^pro) was evaluated using fluorescence resonance energy transfer assay (FRET-based assay). Based on 1D and 2D spectroscopic techniques, compounds (1–18) were identified as 24-β-ethyl-cholesta-5(6),22(23),25(26)-triene-3-ol (1), α-amyrin (2), linoleic acid (3), 24-β-ethyl-cholesta-5(6),22(23),25(26)-triene-3-O-β-d-glucoside (4), 1,3-propanediol-2-amino-1-(3′,4′-methylenedioxyphenyl) (5), (−)-(7R,8R,8′R)-acuminatolide (6), (+)-piperitol (7), 5,7,4′-trihydroxy-8,3′-dimethoxy flavanone (8), 5,7,4′-trihydroxy-6-methoxy flavanone (9), 4′,5-dihydroxy-3′,7,8-trimethoxyflavone (10), 5,7-dihydroxy-3′,4′,5′,8-tetramethoxy flavone (11), 1,3-propanediol-2-amino-1-(4′-hydroxy-3′-methoxyphenyl) (12), 3′,5′,5,7-tetrahydroxy-6-methoxyflavanone (13), simplexoside (piperitol-O-β-d-glucoside) (14), pinoresinol monomethyl ether-β-d-glucoside (15), orientin (16), luteolin-3′-O-β-d-glucoside (17), and 3,5-dicaffeoylquinic acid (18). Compounds 6, 12, and 14 showed comparable inhibitory activities against SARS-CoV-2 M^pro with IC₅₀ values of 0.917 ± 0.05, 0.476 ± 0.02, and 0.610 ± 0.03 μM, respectively, compared with the control lopinavir with an IC₅₀ value of 0.225 ± 0.01 μM. The other tested compounds showed considerable inhibitory activities. The molecular docking study for the tested compounds was carried out to correlate their binding modes and affinities for the SARS-CoV-2 M^pro enzyme with the in vitro results. Analyzing the results of the in vitro assay together with the obtained in silico results led to the conclusion that phenylpropanoids, lignans, and flavonoids could be considered suitable drug leads for developing anti-COVID-19 therapeutics. Moreover, the phenylpropanoid skeleton oxygenated at C3, C4 of the phenyl moiety and at C1, C3 of the propane parts constitute an essential core of the SARS-CoV-2 M^pro inhibitors, and thus could be proposed as a scaffold for the design of new anti-COVID-19 drugs.

Compounds isolated and identified from Helichrysum bracteatum leaves showed promising in vitro inhibitory activities against SARS-CoV-2 main protease (M^pro). Thus, could be considered suitable drug leads for developing anti-COVID-19 therapeutics.     

A New Cephalosporin with a Dual Mode of Action

A cephalosporin, (6R,7R)-7-[(2R)-2-hydroxy-2-phenylacetamido]-3-(pyrid-2-yl-N-oxide) thiomethylceph-3-em-4-carboxylic acid (MCO), that could lead to a novel approach to the problem of β-lactamase destruction is described. The compound is slightly more resistant to some β-lactamases than is cephalothin, but it is still hydrolyzed by many to a varying degree. Hydrolysis of the β-lactam bond of a cephalosporin releases the 3-substituent, which in MCO is itself an antibacterial agent, 2-mercaptopyridine-N-oxide. Thus, MCO has a dual mode of action, and bacteria that do not produce an effective amount of a β-lactamase are inhibited by the intact cephalosporin, whereas those that do hydrolyze it are inhibited by the released antibacterial compound.     

Neuroinflammatory inhibitors from Gardneria nutans Siebold & Zuccarini

Two new monoterpene indole alkaloid glycosides nutanoside A–B (1–2), two new phenolic glycoside esters nutanester A–B (6–7), together with five known compounds (3–5, 8–9) were isolated from the ethanol extract of Gardneria nutans Siebold & Zuccarini. Their structures were established on the basis of extensive spectroscopic analysis and TDDFT/ECD calculations. Compounds 1 and 2 are two rare monoterpene indole alkaloids with the glucosyl moiety located at C-12 and represent the first two examples of enantiomer of ajmaline type monoterpene indole alkaloids. Compounds 3, 4 and 6 displayed significant inhibitory effects on NO production in over-activated BV2 microglial cells, with the IC₅₀ values of 2.29, 6.36, and 8.78 μM, respectively. Compounds 1, 5, 7 could significantly inhibit the mRNA expression of inflammatory factors TNF-α and IL-6 induced by LPS in BV2 microglial cells at the effective concentration. Moreover, compound 3 exhibited stronger cytotoxicities against U87 and HCT116 cell lines than taxol with IC₅₀ values of 10.58 and 14.60 μM, respectively.

Four new compounds were isolated from G. nutans. Compounds 1–2 are two rare monoterpene indole alkaloids with the glucosyl moiety located at C-12 and represent the first two examples of enantiomer of ajmaline type monoterpene indole alkaloids.