Antiviral Activities in Extracts of Turkish Medicinal Plants

A total of 16 ethanol extracts of Turkish medicinal plants were evaluated for antiviral activities against herpes simplex virus (HSV) and Sindbis virus (SINV). Extracts of Galanthus elwesii and Rheum ribes showed the most potent anti-HSV activities, while six other extracts had weaker activities. Galanthus elwesii and Leucojum aestivum were the most potent anti-SINV extracts with four others showing weaker activities. In total, five extracts were active against both viruses, three were selective for HSV and one was selective for SINV. Evidence for an antiviral photosensitizer was obtained in two anti-HSV extracts, in which activity was either completely dependent on light, or was con-siderably enhanced by light. Thus, several Turkish medicinal plants appear to be promising sources of antiviral activities.     

Antiviral activities in extracts of Turkish medicinal plants

A total of 16 ethanol extracts of Turkish medicinal plants were evaluated for antiviral activities against herpes simplex virus (HSV) and Sindbis virus (SINV). Extracts of Galanthus elwesii and Rheum ribes showed the most potent anti-HSV activities, while six other extracts had weaker activities. Galanthus elwesii and Leucojum aestivum were the most potent anti-SINV extracts with four others showing weaker activities. In total, five extracts were active against both viruses, three were selective for HSV and one was selective for SINV. Evidence for an antiviral photosensitizer was obtained in two anti-HSV extracts, in which activity was either completely dependent on light, or was con-siderably enhanced by light. Thus, several Turkish medicinal plants appear to be promising sources of antiviral activities.     

In vitro antiviral activity of Brazilian plants (Maytenus ilicifolia and Aniba rosaeodora) against bovine herpesvirus type 5 and avian metapneumovirus

Context: Medicinal plants are well known for their use in traditional folk medicine as treatments for many diseases including infectious diseases.

Objective: Six Brazilian medicinal plant species were subjected to an antiviral screening bioassay to investigate and evaluate their biological activities against five viruses: bovine herpesvirus type 5 (BHV-5), avian metapneumovirus (aMPV), murine hepatitis virus type 3, porcine parvovirus and bovine respiratory syncytial virus.

Materials and methods: The antiviral activity was determined by a titration technique that depends on the ability of plant extract dilutions (25 or 2.5 µg/mL) to inhibit the viral induced cytopathic effect and the extracts’ inhibition percentage (IP).

Results: Two medicinal plant species showed potential antiviral activity. The Aniba rosaeodora Ducke (Lauraceae) extract had the best results, with 90% inhibition of viral growth at 2.5 µg/mL when the extract was added during the replication period of the aMPV infection cycle. The Maytenus ilicifolia (Schrad.) Planch. (Celastraceae) extracts at a concentration of 2.5 µg/mL exhibited antiviral activity during the attachment phase of BHV-5 (IP = 100%).

Discussion and conclusion: The biomonitored fractionation of the active extracts from M. ilicifolia and A. rosaeodora could be a potential tool for identifying their active compounds and determining the exact mechanism of action.     

Screening of Spanish Medicinal Plants for Antioxidant and Antifungal Activities

Abstract

Dichloromethane, ethyl acetate, methanol, and aqueous extracts obtained from 16 Spanish medicinal plants were screened for their antioxidant and antifungal activities. The radical scavenging capacity was evaluated by the DPPH method using a rapid screening by TLC and a spectrophotometric assay. Polar extracts obtained from Jasonia glutinosa L. (Lamiaceae), Tanacetum parthenium (L.) Schultz (Lamiaceae), Equisetum telmateia Ehrh. (Equisetaceae), Verbena officinalis L. (Verbenaceae), and Lythrum salicaria L. (Lythraceae) showed high antioxidant properties. Among them, the methanol extract of Lythrum salicaria showed the strongest antiradical capacity with an IC₅₀ value similar to the positive control ascorbic acid. On the contrary, the best antifungal properties against Rhizopus stolonifer were produced by ethyl acetate or dichloromethane extracts from Anthemis arvensis L. subsp. arvensis (Asteraceae), Tanacetum parthenium, Santolina chamaecyparissus L. subsp. squarrosa Nyman (Asteraceae), Anagallis arvensis L. (Primulaceae) and the methanol extract of Anagallis foemina Miller (Primulaceae). The dichloromethane extract of Anthemis arvensis subsp. arvensis was the best inhibitor of fungus growth.     

Antimicrobial Activities of Malaysian Plant Species

Antimicrobial activities against reference Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and Candida albicans were tested on 191 plant extracts obtained from more than 30 families of plants found in the state of Sabah, Malaysia. The plant extracts were tested by a disk-diffusion technique in which antimicrobial activity was evaluated based on the ability of the plant extracts to diffuse through agar to affect the target organisms. The extracts of Callicarpa erioclona Schau. (Verbenaceae), Callicarpa farinosa Roxb. (Verbenaceae), Sphonodesma friflora Wright (Verbenaceae), and Homalium panayanum F. Villar (Flacourticeae) exhibited antimicrobial properties worthy of further investigation.     

Activity of acetone and methanol extracts from thirty-one medicinal plant species against herpes simplex virus types 1 and 2

Context: Thirty-one medicinal plant species from Hawaii, Morocco, and the Sonoran Desert, USA have been shown in past studies to be highly inhibitory to pathogenic bacteria, fungi, and certain cancer cell lines. However, none were tested for antiviral activity.

Objective: Acetone and methanol extracts from these species were bio-assayed for antiviral activity against herpes simplex virus types 1 and 2, and for cytotoxicity to the Vero C1008 cell line.

Materials and methods: Extracts from these species were tested in vitro for antiviral activity using an immunoperoxidase mini-plaque reduction assay to detect viral structural protein synthesis. A 50% inhibitory concentration (IC₅₀) was computed. Sulforhodamine B and neutral red assays were used to qualitatively and quantitatively assess the cytotoxicity of extracts to C1008 cells, and to compute a 50% cytotoxic concentration (CC₅₀) using a dose response curve.

Results: Eight of the 31 plant species assayed showed significant antiviral activity against HSV 1 and HSV 2 viruses. The acetone extract of Kalanchoe pinnata Pers. (Crassulaceae) produced an IC₅₀ of 0.025?mg/mL and a CC₅₀ of 1.25?mg/mL yielding a therapeutic index of 50. Additionally, this extract reduced plaque numbers to zero or near zero at a concentration of 0.1?mg/mL when added 30?min before or 30?min after virus infection.

Discussion and conclusion: The mechanism of inhibition against HSV 1 and HSV 2 viruses is now being investigated, along with fractionation of the acetone extract in search of the active compound or compounds.     

Assessment of in vitro antipsoriatic activity of selected Indian medicinal plants

Abstract

Context: Phyllanthus simplex Retz. (Phyllanthaceae), Crotolaria juncea Linn. (Leguminosae), Leucas aspera Linn. (Lamiaceae), and Vitex glabrata R.Br. (Verbenaceae) are well-known Indian medicinal plants. Different parts of these plants are used for healing purposes traditionally in the treatment of psoriasis and various other disorders. This prompted us to assess the antipsoriatic activities of these plants.

Objectives: Petroleum ether and ethanol extracts of the selected plants, i.e., P. simplex (whole plant), C. juncea (seeds), L. aspera (aerial parts), and V. glabrata (leaves) were investigated for their in vitro antipsoriatic activity.

Materials and methods: Antipsoriatic activity of the extracts was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, using HaCaT cells. About 200?µl of different concentrations (25, 50, 100, 200, and 400?µg/ml) of test samples were prepared in the cell culture medium and incubated for 24?h before MTT assay to determine the viable cells. The effect of these extracts on nitric oxide (NO) production and lipid peroxidation was also evaluated.

Results: Our findings revealed that these plants showed promising skin keratinocyte antiproliferative activity. However, the petroleum ether extract of C. juncea (CJPE) and ethanol extract of L. aspera (LAEE) were found to exhibit significant activity (IC₅₀ value?=?45.45 and 55.36?µg/ml, respectively).

Discussion and conclusions: The inhibitory action against NO production and lipid peroxidation in HaCaT cells suggested that the antipsoriatic activity of the extracts was mediated by an antioxidant mechanism. These findings validate the claims of the use of these plants in the treatment of psoriasis.     

Anti-Helicobactor pylori activity of some Jordanian medicinal plants

Context: Natural flora are considered a major source of new agents for the treatment of Helicobactor pylori. The plants used in this study were selected based on previous traditional use.

Objective: In this study, we evaluated the effect of extracts of 16 medicinal plants grown in Jordan against clinical isolates of H. pylori.

Materials and methods: Tested plant extracts included Aloysia triphylla (L'Her.) Britton (Verbenaceae), Anethum graveolens L. (Apiaceae), Artemisia inculata Delile (Asteraceae), Capparis spinosa L. (Capparaceae), Crataegus aronia (L.) Bosc ex. DC. (Rosaceae), Inula viscose (L.) Ait (Asteraceae), Lavandula officinalis Chaix. (Lamiaceae), Lepidium sativum L. (Cruciferae), Origanum syriaca L. (Lamiaceae), Paronychia argentea Lam. (Caryophyllaceae), Passiflora incarnate L. (Passifloraceae), Psidium guajava L. (Myrtaceae), Sarcopoterium spinosum (L.) Spach (Rosaceae), Sesamum indicum L. (Pedaliaceae), Urtica urens L. (Urticaceae) and Varthemia iphionoids Boiss (Asteraceae). Clinical isolates of H. pylori were tested in vitro for susceptibility to each of the above plant crude extracts using disk diffusion method, and the MIC value was determined for each plant extract using the serial dilution method.

Results: Results showed that ethanol extracts of most medicinal plants exerted cytotoxiciy against H. pylori isolates. Among the tested plant extracts, A. triphylla (MIC: 90?µg/mL, MBC: 125?µg/mL) and I. viscosa (MIC: 83?µg/mL, MBC: 104?µg/mL) showed the strongest activity against both isolates of H. pylori.

Discussion and conclusion: Jordanian medicinal plants might be valuable sources of starting materials for the synthesis of new antibacterial agents against H. pylori.     

Further Iinvestigations on the Antiviral Activities of Medicinal Plants of Togo

Further studies were done on the antiviral activities of 10 species of Togolese medicinal plants, previously shown to possess activity against herpes simplex virus (HSV). The dominant activity in all cases was virucidal (direct inactivation of virus particles), although Adansonia digitata extracts also appeared to have intracellular antiviral activities as well, which could indicate the presence of multiple antiviral compounds, or a single compound with multiple actions. In the seven most active extracts, the anti-HSV activity was considerably enhanced by light, especially UVA (long wavelength UV), although they all showed “dark” antiviral activity as well. Thus, all the extracts contained antiviral photosensitizers. In all tests, the root-bark and leaf extracts of A. digitata were the most potent.     

Further iinvestigations on the antiviral activities of medicinal plants of togo

Further studies were done on the antiviral activities of 10 species of Togolese medicinal plants, previously shown to possess activity against herpes simplex virus (HSV). The dominant activity in all cases was virucidal (direct inactivation of virus particles), although Adansonia digitata extracts also appeared to have intracellular antiviral activities as well, which could indicate the presence of multiple antiviral compounds, or a single compound with multiple actions. In the seven most active extracts, the anti-HSV activity was considerably enhanced by light, especially UVA (long wavelength UV), although they all showed "dark" antiviral activity as well. Thus, all the extracts contained antiviral photosensitizers. In all tests, the root-bark and leaf extracts of A. digitata were the most potent.     

Multiple Antiviral Activities of Endemic Medicinal Plants Used by Berber Peoples of Morocco

We investigated the antiviral activities of methanol extracts of 75 Moroccan plants (64 genera of 35 families), used traditionally to treat diseases that could be caused by viruses and microbes. The plants included many endemic to Morocco and used by Berber as well as Arab peoples. They were evaluated against three mammalian viruses: herpes simplex virus, Sindbis virus and poliovirus, at non-cytotoxic concentrations. Five extracts were very active against the three viruses, 16 were active against two viruses, and 24 were only active against one virus. Thirty-two extracts showed light enhanced and two showed light-dependent activities. Punica granatum extract, which was the most active, inhibited all three viruses at a concentration of only 1.5 µg/ml, although these activities were not light enhanced. The extracts of Acacia gummifera, Juglans regia, Thymus maroccanus, Lawsonia inermis, Pinus halepensis, and Rosa canina inhibited Sindbis virus at a minimum concentration of 1.5 µg/ml. Thymus maroccanus and Rosa canina activities were light enhanced. Pistacia lentiscus and Thymus maroccanus were very active against herpes simplex virus. The extracts most active against poliovirus were those from Pinus halepensis and Punica granatum. These were active at minimum concentrations of 6.5 µg/ml, but were not light enhanced. These results indicate that some of these plants are potential potent medicines against infectious diseases caused by viruses. Their discriminatory effect against specific microorganisms suggests the presence of different chemical compounds. Light is a determining factor in the activity of photosensitizers and should be definitely taken into account in this kind of test.     

Antimycoplasmal activity of some plant species from northern Nigeria compared to the currently used therapeutic agent

Context:?Mycoplasma spp. are obligate parasites of humans and animals. But due to the special requirements needed to culture Mycoplasma in the laboratory, little or no research has been done to evaluate the efficacy of medicinal plants on the organism.

Objective:?To screen medicinal plants traditionally used to treat infections for possible antimycoplasmal and cytotoxic activities.

Materials and methods:?Acetone extracts of 21 Nigerian medicinal plants were analyzed for antimycoplasmal and cytotoxicity activities using the metabolic inhibition and colorimetric methods, respectively. The extract with the best antimycoplasmal activities was also analyzed for its phytochemical constituents using the desktop method.

Results:?Calotropis procera (Aiton) R.Br (Asclepiadaceae) extract had the best antimycoplasmal effect with a minimum inhibitory concentration (MIC) of 80 µg/mL and minimum mycoplasmacidal concentration (MMC) of 160 µg/mL. This extract contained saponins, tannins, cardiac glycosides, alkaloids, and flavonoids. The extract of Vernonia amygdalina Delile (Compositae) was the most cytotoxic with median lethal concentration (LC₅₀) of approximately 17 µg/mL, and that of Anacardium occidentale L. (Anacardiaceae) was the least cytotoxic with an LC₅₀ of approximately 1919 µg/mL.

Discussion:?Calotropis procera is a promising plant for an alternative antimycoplasmal agent because the crude acetone extract had a higher mycoplasmacidal activity than the conventional drug tylosin, which is currently used in treatment of the disease in Nigeria.

Conclusion:?The crude extract of Calotropis procera is worth investigating for the development of a potent agent against cattle Mycoplasma, which has long defied solution by conventional chemotherapy.     

Protective effect of partially purified 35 kDa protein from silk worm (Bombyx mori) fecal matter against carbon tetrachloride induced hepatotoxicity and in vitro anti-viral properties

Context: It has been found that many proteins from silkworm (Bombyx mori L.) fecal matter have been active against human immunodeficiency virus, Sendai virus, herpes simplex virus type-1, and nuclear polyhedrosis virus.

Objective: A partially purified 35?kDa protein from silkworm was screened for its hepatoprotective activity, and in vitro antioxidant, and antiviral properties against camelpox and goatpox viruses.

Materials and methods: The study investigated the efficiency of the partially purified 35kDa protein from silk worm fecal matter against CCl₄-induced liver damage measured in terms of enzyme levels such as aspartate aminotransferase (AST), alanine amino transferase(ALT), alkaline phosphatase (ALP) and total bilirubin, which maintain liver integrity. In vitro antioxidant potential of this protein was determined based on its ability to scavenge 2, 2-diphenylpicrylhydrazyl (DPPH) and superoxide anions scavenging activity. Further, in vitro cytotoxic effect on Vero cells and antiviral activity against goatpox and camelpox viruses were also studied.

Results: The protein had significant hepatoprotection against CCl₄-induced liver damage and scavenging of DPPH radical and superoxide anion activity. However, the protein did not inhibit the multiplication of either virus tested at its maximum non-toxic concentration (MNTC) in vitro.

Discussion and conclusion: The partially purified 35?kDa protein from silk worm Bombyx mori L fecal matter possessed protective effect against CCl₄-induced oxidative stress in rat model. The protein was found to be ineffective against camelpox and goatpox viruses at its MNTC in vitro.     

Investigation of Medicinal Plants of Togo for Antiviral and Antimicrobial Activities

Methanol extracts were prepared from 19 medicinal plants of Togo and, by means of standard laboratory tests, were analysed for antiviral and antibiotic activities. Ten of the 19 showed significant antiviral activity and all but two displayed antibiotic activity. Extracts of three species, Adansonia digitata (the most potent), Conyza aegyptiaca and Palisota hirsuta , were active against all three test viruses (herpes simplex, Sindbis and poliovirus). The other seven, however, were more selective, showing activity against only one or two viruses. The antibiotic profiles varied considerably. The observation that each extract showed a distinctive permutation of target organisms suggests that different bioactive phytochemicals are present in each species. Only two of the extracts were devoid of bioactivity.     

Investigation of medicinal plants of togo for antiviral and antimicrobial activities

Methanol extracts were prepared from 19 medicinal plants of Togo and, by means of standard laboratory tests, were analysed for antiviral and antibiotic activities. Ten of the 19 showed significant antiviral activity and all but two displayed antibiotic activity. Extracts of three species, Adansonia digitata (the most potent), Conyza aegyptiaca and Palisota hirsuta , were active against all three test viruses (herpes simplex, Sindbis and poliovirus). The other seven, however, were more selective, showing activity against only one or two viruses. The antibiotic profiles varied considerably. The observation that each extract showed a distinctive permutation of target organisms suggests that different bioactive phytochemicals are present in each species. Only two of the extracts were devoid of bioactivity.     

In vivo and in vitro antiviral activity of five Tibetan medicinal plant extracts against herpes simplex virus type 2 infection

Extracts from five Tibetan medicinal plants collected from the Tibetan Plateau were evaluated for antiviral activity against herpes simplex virus type 2 (HSV-2) in vitro and in vivo. Viral plaque reduction assays showed that extracts from four out of five plants inhibited HSV-2 infection significantly with 50% effective concentrations (EC₅₀) values ranging from 0.35?±?0.11 to 1.83?±?0.21?mg/mL. The other plant, Swertia mussotii Franch. (Gentianaceae), exhibited activity in inhibiting the viral biosynthesis. In the attachment assay, two plants, Dracocephalum heterophyllum Benth. (Lamiaceae) and Dracocephalum tanguticum Maxim. (Lamiaceae) reduced the attachment of HSV-2 to cell surface. Interestingly, all of the extracts showed virucidal activity. Analyzed by real-time PCR, three extracts showed strong inhibition of HSV DNA replication with Dracocephalum heterophyllum and Dracocephalum tanguticum at the concentration of 4?mg/mL and Lagotis brevituba Maxim. (Scrophulariaceae) at 1?mg/mL. BALB/c mice were used for determining in vivo efficacy. Mice encephalitis herpes models were established by infection with HSV-2. The extracts of Dracocephalum heterophyllum, Dracocephalum tanguticum, and Swertia mussotii at a dose of 1?g/kg per day significantly prolonged the mean survival times and reduced the mortality of HSV-2 infected mice compared with control group (P?<?0.05). Taken together, we conclude that the antiviral mechanisms of these plants involve various stages of virus replication. Extracts from three of these plants, Dracocephalum heterophyllum, Dracocephalum tanguticum, and Swertia mussotii, may be possible candidates in developing anti-HSV-2 medicine.     

Assessment of selected Yemeni medicinal plants for their in vitro antimicrobial,anticancer, and antioxidant activities

Context: The role of natural products as a source for remedies has been recognized since the beginning of mankind. Nevertheless, a minority of folkloricly used medicinal plants have been evaluated for their pharmacological activities.

Objectives: The purpose of this study is to evaluate 33 selected Yemeni plants for their in vitro anticancer, antimicrobial, and antioxidant activities.

Materials and methods: The plants were extracted with methanol and hot water. The obtained 66 extracts were tested for their in vitro cytotoxic activity using the neutral red uptake assay against two cancer cell lines (5637 and MCF-7). The antimicrobial activity was determined using the agar diffusion method and MIC-determination. The DPPH radical method was used for the determination of antioxidant activity.

Results: Interesting cytotoxic activity was observed for Hypoestes forskalei (Vahl) R. Br. (Acanthaceae), Lycium shawii Roem. & Schult. (Solanaceae), Pergularia tomentosa L. (Asclepiadaceae), Psiadia punctulata (DC.) Vatke (Compositae), Pulicaria petiolaris Jaub. & Spach (Compositae) and Rosmarinus officinalis L. (Labiatae) (IC₅₀ values < 50 μg/mL). Antimicrobial activity with MIC values ≤ 125 μg/mL was exhibited against Gram-positive bacteria by Chrozophora oblongifolia (Del.) A.Juss. ex Spreng. (Euphorbiaceae), Myrtus communis L. (Myrtaceae), Phragmanthera regularis (Steud. ex Sprague) M.G. Gilbert (Loranthaceae) and R. officinalis. Antioxidant activity was observed for C. oblongifolia, M. communis, and P. regularis.

Conclusion: The results justified the use of some investigated plants in the Yemeni ethnomedicine. These findings demonstrated that some of the investigated plants could be a source of new cytotoxic and antibiotic compounds; however, further work is needed.     

Antiviral activities of extracts and selected pure constituents of Ocimum basilicum

1. Ocimum basilicum (OB), also known as sweet basil, is a well known medicinal herb in traditional Chinese medicine preparations. In the present study, extracts and purified components of OB were used to identify possible antiviral activities against DNA viruses (herpes viruses (HSV), adenoviruses (ADV) and hepatitis B virus) and RNA viruses (coxsackievirus B1 (CVB1) and enterovirus 71 (EV71)). 2. The results show that crude aqueous and ethanolic extracts of OB and selected purified components, namely apigenin, linalool and ursolic acid, exhibit a broad spectrum of antiviral activity. Of these compounds, ursolic acid showed the strongest activity against HSV-1 (EC50 = 6.6 mg/L; selectivity index (SI) = 15.2), ADV-8 (EC50 = 4.2 mg/L; SI = 23.8), CVB1 (EC50 = 0.4 mg/L; SI = 251.3) and EV71 (EC50 = 0.5 mg/L; SI = 201), whereas apigenin showed the highest activity against HSV-2 (EC50 = 9.7 mg/L; SI = 6.2), ADV-3 (EC50 = 11.1 mg/L; SI = 5.4), hepatitis B surface antigen (EC50 = 7.1 mg/L; SI = 2.3) and hepatitis B e antigen (EC50 = 12.8 mg/L; SI = 1.3) and linalool showed strongest activity against AVD-II (EC50 = 16.9 mg/L; SI = 10.5). 3. No activity was noted for carvone, cineole, beta-caryophyllene, farnesol, fenchone, geraniol, beta-myrcene and alpha-thujone. 4. The action of ursolic acid against CVB1 and EV71 was found to occur during the infection process and the replication phase. 5. With SI values greater than 200, the potential use of ursolic acid for treating infection with CVB1 and EV71 merits further investigation.     

In vitro anti-herpes simplex viruses and anti-adenoviruses activity of twelve traditionally used medicinal plants in Taiwan

As an effort to search for new antiviral agents from traditional medicine, the hot water (HW) extract of twelve traditionally used medicinal plants in Taiwan was evaluated for their in vitro anti-herpes simplex viruses (HSV; including HSV-1 and HSV-2) and anti-adenoviruses (ADV; including ADV-3, ADV-8 and ADV-11) activities with a XTT-based colorimetric assay. Results showed that the tested HW extracts exhibited anti-HSV and anti-ADV activities at different magnitudes of potency. Among the twelve medicinal plants, Boussingaultia gracilis var. pseudobaselloides (Basellaceae) and Serissa japonica (Rubiaceae) possessed broad spectrum of antiviral activity. Ardisia squamulosa (Myrsinaceae) and Artemisai princeps var. orientalis (Compositae) were more effective in inhibiting ADV-8 replication than the other four viruses. Cell cytotoxic assay demonstrated that all tested HW extracts had CC50 values higher than their EC50 values. It was concluded that the twelve traditionally used medicinal plants in Taiwan possessed antiviral activity, and some of them merit further investigation.     

Synthesis and antiviral activity of some novel indole-2-carboxylate derivatives

A series of novel indole-2-carboxylate derivatives were synthesized and assayed to determine their in vitro broad-spectrum antiviral activities. The biological results showed that some of the synthesized compounds exhibited potent broad-spectrum antiviral activity. Notably, compound 8f showed the highest SI value (17.1) to Cox B3 virus. Compound 14f showed both potent inhibitory activity against influenza A (IC₅₀=7.53 μmol/L) and the highest SI value (12.1). SAR results showed that the alkyloxy at the 4-position of indole ring was not crucial to the antiviral activities. Incorporation of an acetyl substituent at the amino group disfavored antiviral activity towards RNA viruses.KEY WORDS: Indole-2-carboxylate, Broad-spectrum antiviral activity, DNA and RNA virus, SAR