Anti-Hepatitis C Virus Activity of a Crude Extract from Longan (Dimocarpus longan Lour.) Leaves

Potential of longan (Dimocarpus longan Lour.) in functional food: A review of molecular mechanism-directing health benefit properties

Longan (Dimocarpus longan Lour.) has received widespread attention worldwide as a therapeutic food with nutritional, economic, and medicinal value. Its fruit, seed, pericarp, and flower becoming dietary tools for health maintenance when it comes to targeting chronic diseases or sub-health conditions. In recent years, research focusing on longan and human health has intensified, and the high-value products of the whole fruit, including polyphenols, polysaccharides, angiotensin-I-converting enzyme (ACE)-inhibiting peptides, gamma-aminobutyric acid (GABA), and Maillard reaction products etc., may have beneficial effects on human health by preventing the onset of chronic diseases and cancer, maintaining intestinal homeostasis and skin health. Here, we review and summarize the new available evidence on the bioactive role of phytochemicals in longan and explore the relationship between longan bioactive compounds and health benefits, with a focus on the molecular mechanisms of the health effects.

P80 natural essence spray and lozenges provide respiratory protection against Influenza A, B, and SARS-CoV-2

Seasonally circulating viruses, such as Influenza, as well as newly emerging viruses and variants thereof, and waning immunity urge the need for safe, easy-to-use and inexpensive drugs to protect from these challenges. To prevent transmission of these viruses and subsequent excessive inflammatory reactions on mucous membranes, we tested the efficacy of the natural essence P80 as spray and in form of lozenges against respiratory infections caused by SARS-CoV-2 variants of concern (VoCs), influenza A (H3N2) and influenza B (Victoria). P80 natural essence, a Dimocarpus longan extract, shielded highly differentiated human airway epithelia from SARS-CoV-2 wildtype and Omicron variant as well as Influenza A and B infection and dampened inflammation by down-modulating pro-inflammatory cytokine and anaphylatoxin secretion. A single application of P80 natural essence spray maintained tissue integrity long-term. This also significantly reduced the release of infectious viral particles and the secretion of IP10, MCP1, RANTES and C3a, all of which mediate the migration of immune cells to the sites of infection. Even P80 lozenges dissolved in distilled water or non-neutralizing saliva efficiently prevented SARS-CoV-2 and Influenza-induced tissue destruction. Consequently, our in vitro data suggest that P80 natural essence can act as antiviral prophylactic, both in form of nasal or oral spray and in form of lozenges, independent of circulating respiratory challenges.

Acacia mangium: A promising plant for isolating anti-hepatitis C virus agents

Background: Medicinal plants are potential resources for isolating drug candidates. Various plants have been reported to possess pharmacological effects including anti-hepatitis C activities. The current study examined the anti-hepatitis C virus (HCV) activities of Acacia mangium extracts in solvents with various polarities and further evaluated the mechanism of action of the extracts using Western blotting and combination treatment models. Methods: The leaves of A. mangium were extracted in two phases, first in ethanol and then in solvents with different polarities (n-hexane, dichloromethane, and methanol). HCV-infected Huh7it-1 cells were treated with the extracts at concentrations of 0.01, 0.1, 1, 10, 50, and 100 µg/mL. Results: The results revealed the strong anti-HCV activities of the extracts. The 50% inhibition concentrations (IC 50s) of the ethanol, n-hexane, dichloromethane and methanol extracts were of 4.6 ± 0.3, 2.9 ± 0.2, 0.2 ± 0.3, and 2.8 ± 0.2 μg/mL, respectively, and no cytotoxic effect was detected. These extracts displayed stronger effects than the positive control ribavirin. The mode of action of the ethanol extract was evaluated at 30 µg/mL, revealing that the inhibitory effect was stronger on the post-entry step than on the entry step. Western blotting revealed that the extracts decreased NS3 protein expression, indicating that virus replication was suppressed. Further evaluation illustrated that combined treatment with the ethanol extract enhanced the anti-viral activity of simeprevir. Conclusions: These results indicated that A. mangium leaves could represent sources of anti-HCV agents.

The long and stumble way to find potential active compounds from plants for defeating hepatitis B and C: review

Hepatitis is a liver illness caused by virus such as hepatitis A virus, hepatitis B virus and hepatitis C virus. Hepatitis B and C are considerably more usual and induce more cirrhosis and dead worldwide than hepatitis A. Although drugs that are currently often used in the medication of hepatitis B and C, the finding of recent drug from various resources including herbal has been intensively developed. Therefore, the purpose of this review is to consider the possibility of plant’s compounds as anti-HBV and anti-HCV. From the results of a review of several articles, several plant’s compound have shown effectiveness againts HBV and HCV by in silico, in vitro and in vivo studies. In conclusion, several plant’s active compounds are possibility to be developed as anti-hepatitis B and C.

Exhaustive Plant Profile of “Dimocarpus longan Lour” with Significant Phytomedicinal Properties: A Literature Based-Review

Background: “Dimocarpus longan Lour” is a tropical and subtropical evergreen tree species mainly found in China, India, and Thailand; this plant, found naturally in Bangladesh, even locally, is used as “kaviraj” medication for treating different diseases, such as gastrointestinal disorders, wounds, fever, snake bites, menstrual problem, chickenpox, bone fractures, neurological disorders, and reproductive health. Different parts of this plant, especially juice pulp, pericarp, seeds, leaves, and flowers, contain a diverse group of botanical phytocompounds, and nutrient components which are directly related to alleviating numerous diseases. This literature-based review provides the most up-to-date data on the ethnomedicinal usages, phytochemical profiling, and bio-pharmacological effects of D. longan Lour based on published scientific articles. Methodology: A literature-based review was conducted by collecting information from various published papers in reputable journals and cited organizations. ChemDraw, a commercial software package, used to draw the chemical structure of the phytochemicals. Results: Various phytochemicals such as flavonoids, tannins, and polyphenols were collected from the various sections of the plant, and other compounds like vitamins and minerals were also obtained from this plant. As a treating agent, this plant displayed many biologicals activities, such as anti-proliferative, antioxidant, anti-cancer, anti-tyrosinase, radical scavenging activity, anti-inflammatory activity, anti-microbial, activation of osteoblast differentiation, anti-fungal, immunomodulatory, probiotic, anti-aging, anti-diabetic, obesity, neurological issues, and suppressive effect on macrophages cells. Different plant parts have displayed better activity in different disease conditions. Still, the compounds, such as gallic acid, ellagic acid, corilagin acid, quercetin, 4-O-methyl gallic acid, and (-)-epicatechin showed better activity in the biological system. Gallic acid, corilagin, and ellagic acid strongly exhibited anti-cancer activity in the HepG2, A549, and SGC 7901 cancer cell lines. Additionally, 4-O-methyl gallic acid and (-)-epicatechin have displayed outstanding antioxidant activity as well as anti-cancer activity. Conclusion: This plant species can be considered an alternative source of medication for some diseases as it contains a potential group of chemical constituents.

P80 Natural Essence Exerts Efficient Anti-HIV-1- as Well as Adjuvant Effects in DCs

Dendritic cells (DCs), as well as complement, play a major role during human immunodeficiency virus 1 (HIV-1) entry and infection at mucosal sites. Together, DCs and complement are key points for understanding host defence against HIV-1 infection and for studying the impact of new drugs on the regulation of innate host-pathogen interactions and adaptive immunity. For this, we evaluated the antiviral effect of the P80 natural essence (Longan extract) on interactions of non- and complement-opsonized HIV-1 with DCs. In viability assays, we first illustrated the effects of P80 natural essence on DC function. We found that P80 concentrations above 1.5% caused increased cell death, while at concentrations between 0.5% and 1% the compound exerted efficient antiviral effects in DCs and illustrated an adjuvant effect regarding DC activation. DC maturation, as well as co-stimulatory capacity, were significantly improved by P80 natural essence via p38 MAPK phosphorylation in presence of the viral challenge independent of the opsonization pattern. These findings might be exploited for future therapeutic options to target DC subsets directly at mucosal sites by P80 natural essence and to block entry of both, non- and complement-opsonized HIV-1.

Alkaloid and benzopyran compounds of Melicope latifolia fruit exhibit anti-hepatitis C virus activities

BACKGROUND

New agents for developing alternative or complementary medicine to treat the hepatitis C virus (HCV) are still needed due to high rates of HCV infection globally and the current limitations of available treatments. Treatment of HCV with a combination of direct acting antivirals have been shown to be approximately 90% effective but will be limited in the future due to the emergence of drug resistance and high cost. The leaves of Melicope latifolia have previously been reported to have anti-HCV activity and are a potential source of bioactive compounds for future novel drug development. This study aimed to evaluate the efficacy of the extract of M. latifolia fruit to treat HCV and to isolate its active compounds.

METHOD

M. latifolia fruit was extracted using methanol and purified using vacuum liquid chromatography (VLC) and Radial Chromatography. The anti-HCV activity was analyzed using cell culture lines Huh7it-1 and JFH1 (genotype 2a). Time-of-addition and immunoblotting studies were performed to identify the mode of action of the isolated active compounds. The structures of the active compounds were determined using nuclear magnetic resonance (NMR) spectra, UV, IR, and Mass Spectra.

RESULTS

Six known compounds were isolated from M. latifolia fruit: O-methyloktadrenolon, alloevodionol, isopimpinellin, alloxanthoxyletin, methylevodionol, and N-methylflindersine. N-methylflidersine was the most active compound with IC50 value of 3.8 μg/ml while methylevodionol, isopimpinellin, and alloevodionol were less active. O-methyloktadrenolon and alloxanthoxyletin were moderately active with IC50 values of 10.9 and 21.72 μg/ml, respectively. N-methylflidersine decreased level of HCV NS3 protein expression in the cells.

CONCLUSION

The alkaloid compound, N-methylflindersine which was isolated from M. latifolia possesses anti-HCV activity through post-entry inhibition and suppressed NS3 protein expression.

Infectivity and viability of dengue virus infected hepatocytes cocultured with peripheral blood mononuclear cells from a healthy subject

BACKGROUND Dengue virus (DENV) can infect and replicate in monocytes, resulting in antibody-dependent enhancement. The liver is the main target of DENV, and the infection mechanisms of DENV include direct cytopathic effects (CPEs) of the virus, mitochondrial dysfunction, and effect of cellular and humoral immune factors in the liver. This study was aimed to explore the infectivity of DENV and viability of human hepatocytes using Huh 7it-1 cells cocultured with peripheral blood mononuclear cells (PBMCs). METHODS Huh 7it-1 cells were infected with dengue virus serotype-2 (DENV-2) New Guinea C strain at multiplicity of infection of 0.5 and 1 FFU/cell, and cocultured in vitro with and without adherent PBMCs. The infectivity of DENV was assessed by immunoperoxidase staining. The viability of Huh 7it-1 cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT, a tetrazole) assay and trypan blue staining. Data were statistically analyzed by Shapiro–Wilk and analysis of variance for normality significances. RESULTS The result showed that addition of PBMCs to DENV-2 infected Huh 7it-1 cells decreased the infectivity of DENV (15–37%). DENV-2 infection decreased the viability of Huh 7it-1 cells (15.5–20.8%). Despite the decrease in infectivity of DENV, the addition of PBMCs increased the Huh 7it-1 cells viability (4.5–10.2%). CONCLUSIONS Addition of PBMCs to Huh 7it-1 cells that are infected with DENV-2 decreased the infectivity of DENV and increased Huh 7it-1 cells viability.

Plants Metabolites: Possibility of Natural Therapeutics Against the COVID-19 Pandemic

COVID-19, a disease induced by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2), has been the cause of a worldwide pandemic. Though extensive research works have been reported in recent days on the development of effective therapeutics against this global health crisis, there is still no approved therapy against SARS-CoV-2. In the present study, plant-synthesized secondary metabolites (PSMs) have been prioritized to make a review focusing on the efficacy of plant-originated therapeutics for the treatment of COVID-19. Plant metabolites are a source of countless medicinal compounds, while the diversity of multidimensional chemical structures has made them superior to treat serious diseases. Some have already been reported as promising alternative medicines and lead compounds for drug repurposing and discovery. The versatility of secondary metabolites may provide novel antibiotics to tackle MDR (Multi-Drug Resistant) microbes too. This review attempted to find out plant metabolites that have the therapeutic potential to treat a wide range of viral pathogens. The study includes the search of remedies belonging to plant families, susceptible viral candidates, antiviral assays, and the mode of therapeutic action; this attempt resulted in the collection of an enormous number of natural therapeutics that might be suggested for the treatment of COVID-19. About 219 plants from 83 families were found to have antiviral activity. Among them, 149 plants from 71 families were screened for the identification of the major plant secondary metabolites (PSMs) that might be effective for this pandemic. Our investigation revealed that the proposed plant metabolites can serve as potential anti- SARS-CoV-2 lead molecules for further optimization and drug development processes to combat COVID-19 and future pandemics caused by viruses. This review will stimulate further analysis by the scientific community and boost antiviral plant-based research followed by novel drug designing.

ANTI HEPATITIS C ACTIVITY AND TOXICITY OF Scoparia dulcis LINN. HERB

Hepatitis C Virus (HCV) infection is a serious public health problem since HCV is the ribonucleic acid (RNA) virus that  easy to mutate. The HCV standard treatment  has rapidly developed but the possibility of resistance and effectiveness of treatment needs to be considered. The medicinal plants are a source of various compounds that may potentially cure diseases including infectious diseases. Since a long years ago, medicinal plants were famous as an inherited treatment that believed to cure the disease. One of the medicinal plants is Scoparia dulcis (S. dulcis) that belongs to Scrophulariaceae family and traditionally used as remedies for digestive problems, hypertension, diabetes mellitus, bronchitis, and as an analgesic & antipyretic agent. The previous report showed that S. dulcis was known active as an antiviral against Herpes Simplex Virus (HSV) type 1 in vitro and in vivo. The aim of the study is to determine the biactivity potential of S. dulcis against HCV. Scoparia dulcis was extracted using 80% ethanol (EE) then further separated by liquid-liquid fractionation using dichloromethane (DCMF), ethyl acetate (EAF), butanol solvent (BF) and water (WF). The in vitro anti-HCV analysis was performed with Huh7it cells and HCV JFH1 (genotype 2a) by determining inhibition concentration 50 (IC50). The toxicity (Cytotoxicity Concentration 50, CC50) test was performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and mechanism of action were analyzed using time addition experiment.   Phytochemical groups as the suspected active compounds of S. dulcis were identified by Thin Layer Chromatography (TLC) and observed under UV 254 nm, UV 365 nm, before and after sprayed using H2SO4 10% and heated at 105oC for 5 minutes. The IC50 test result of 80% EE and DCMF showed anti-HCV activity with a value of 12.7±4.8 µg/ml and 5.8±0.69 µg/ml, while EAF, BF, and AF respectively resulted in IC50 value of  >100 µg/ml that suggested there was no inhibition effect on HCV JFH1.  The DCMF was the most active fraction but toxic to the cell with CC50 value >23 µg/ml and selectivity index (SI) >3.9. According to the time addition experiment data, DCMF of S. dulcis inhibited post entry step HCV JFH1 infection that it means the possibility was to inhibit virus replication and or virion release. Scoparia dulcis contain chlorophyll, flavonoids and terpenoids as the suspected active compounds for inhibition of HCV JFH1 infecton. Futher study of post-entry inhibitions of HCV infection was needed.

Longan fruit increase bone mineral density in zebrafish and ovariectomized rat by suppressing RANKL-induced osteoclast differentiation

BACKGROUND

The receptor activator of nuclear factor-kappa B ligand (RANKL)-induced nuclear factor-kappa B (NF-κB) signaling pathway plays essential roles in osteoclast differentiation and may serve as an attractive target for the development of therapeutics for osteoporosis.

PURPOSE

This study aimed to identify plant extracts that attenuated RANKL-induced NF-κB signaling pathway and examine their anti-osteoporotic effects in animal model systems.

METHODS

Osteoclast differentiation was determined by western blot analysis, RT-PCR, and tartrate-resistant acid phosphatase (TRAP) assay. The effect of Longan (Dimocarpus longan Lour.) fruit extract (LFE) on bone mineral density was evaluated by calcein staining in zebrafish and micro-CT analysis in ovariectomized (OVX) rat.

RESULTS

LFE nullified RANKL-induced down-regulation of inhibitor of NF-κB, which keeps NF-κB sequestered in the cytosol, thereby inhibiting translocation of NF-κB to the nucleus, in RAW264.7 cells. In addition, LFE decreased the nuclear levels of c-Fos and nuclear factor of activated T-cells c1, which play crucial roles in RANKL-induced osteoclast differentiation, in RAW264.7 cells. LFE repressed RANKL-activated cathepsin K and TRAP expression in RAW264.7 cells, resulting in a reduction of the number of TRAP-positive multinucleated cells, without cytotoxicity. Furthermore, LFE increased bone mineralization in zebrafish and prevented bone loss in OVX rat.

CONCLUSION

Collectively, our findings suggest that LFE exerts its anti-osteoporotic activity through inhibition of osteoclast differentiation and may have potential as a herbal therapeutic or preventive agent for the treatment of osteoporosis.

Antiviral Activities of Curcuma Genus against Hepatitis C Virus

Hepatitis C virus (HCV) infection is one of the major public health problems in the world. Even though the new agents are shown to increase the sustained virology response, however, there are still many people who cannot access the therapy due to the high cost. Moreover, the emergence of resistance and side effects presented the necessity to develop alternative treatment agents for HCV infection. Plants of the genus of curcuma are popular among traditional medicines in the world, including Indonesia. They have been used for many herb remedies and reported to possess many biological activities. Several plants from the curcuma genus were known as treatment agents in liver disease and jaundice. Our current study determines antiviral activities of Curcuma domestica, Curcuma xanthorrhiza, and Curcuma heyneana against HCV and further examines the mechanism of actions. Antiviral activity was performed by in vitro culture cells using Huh 7.5it cells and treated with the mixture of extract and virus JFH1. The effects of extracts in HCV life cycle were determined by mode of action analysis to examine the action of substances in the entry or post entry steps. The results revealed that ethanol extract of C. domestica, C. xanthorrhiza, and C. heyneana showed strong anti-HCV activities with IC50 values of 1.68 ± 0.05, 4.93 ± 0.42 and 5.49 ± 0.59 μg/mL, respectively without any cytotoxicity effect. Mode of action analysis demonstrated that of C. domestica and C. heyneana exhibit HCV in the entry step, while C. xanthorrhiza inhibit in the entry and post entry steps of HCV life cycle. Docking analysis to predict the interaction of curcumin, the main compound of curcuma genus, revealed a strong interaction between curcumin and 4GAG receptor, a protein involved in the entry step of HCV infection. Moreover, it was also reported to possess good interaction with 4EAW, an HCV NS5B, which plays an important role in HCV replication. These results suggested that C. domestica, C. xanthorrhiza, and C. Heyneana possessed strong inhibition against hepatitis C virus, therefore they may be good candidates for anti-HCV agents.

Virucidal and Neutralizing Activity Tests for Antiviral Substances and Antibodies

In a narrow definition, virucidal activity represents the activity by which to interact with and physically disrupt viral particles. In a broad definition, it includes the activity by which to functionally inhibit (neutralize) viral infectivity without apparent morphological alterations of the viral particles. The viral infectivity can be measured in cell culture system by means of plaque assay, infectious focus assay, 50% tissue culture infectious dose (TCID₅₀) assay, etc. Morphologically, disruption of viral particles can be demonstrated by negative staining electron microscopic analysis of viral particles. In this article, we describe methods to assess virucidal activity in a broad definition.

Antiviral effect of <em>Archidendron pauciflorum</em> leaves extract to hepatitis C virus: An <em>in vitro</em> study in JFH-1 strain

Background: Hepatitis C virus (HCV) is a leading cause of chronic liver diseases. Drug resistance to the regimen is also increasing. Hence, there is a need for new anti-HCV agents that are less toxic and more efficacious. The aim of this study is to evaluate the  possibility of A. pauciflorum extracts can be a antiviral drug.Methods: Huh-7it cells were infected with the HCV genotype 2a strain JFH-I in the presence of methanol extracts of Archidenron pauciflorum. The methanol extract further partition used n-hexane, ethyl acetate, n-butanol, and water showed in which butanol extracts exerted the strongest IC50 (6.3 g/ml). Further, the butanol fraction was fractionated and yielded into 13 fractions.Results: The methanol extract of the leaves of A. pauciflorum exhibited concentration dependent inhibition against the JFH1 strain of HCV genotype 2a with an IC50 is 72.5 μg/ml. The butanol fraction exhibited the highest anti-HCV activity with an IC50 is 6.3 μg/ml. The butanol fraction was fractionated which yielded 13 fractions. Fractions 5 and 13 exhibited high anti-HCV activities with IC50 is 5.0 μg/ml and 8.5 μg/ml and a time-of-addition study demonstrated that fraction 5 inhibited viral infection at the post-entry step, whereas fraction 13 primarily inhibited the viral entry step.Conclusion: The extract A. pauciflorum can be used as a herbal-based antiviral drug.

Time-of-addition and Temperature-shift Assays to Determine Particular Step(s) in the Viral Life Cycle that is Blocked by Antiviral Substance(s)

Viruses infect their host cells to produce progeny virus particles through the sequential steps of the viral life cycle, such as viral attachment, entry, penetration and post-entry events. This protocol describes time-of-addition and temperature-shift assays that are employed to explore which step(s) in the viral life cycle is blocked by an antiviral substance(s).

Broad-spectrum antiviral agents: secreted phospholipase A2 targets viral envelope lipid bilayers derived from the endoplasmic reticulum membrane

Hepatitis C virus (HCV), dengue virus (DENV) and Japanese encephalitis virus (JEV) belong to the family Flaviviridae. Their viral particles have the envelope composed of viral proteins and a lipid bilayer acquired from budding through the endoplasmic reticulum (ER). The phospholipid content of the ER membrane differs from that of the plasma membrane (PM). The phospholipase A2 (PLA2) superfamily consists of a large number of members that specifically catalyse the hydrolysis of phospholipids at a particular position. Here we show that the CM-II isoform of secreted PLA2 obtained from Naja mossambica mossambica snake venom (CM-II-sPLA2) possesses potent virucidal (neutralising) activity against HCV, DENV and JEV, with 50% inhibitory concentrations (IC50) of 0.036, 0.31 and 1.34 ng/ml, respectively. In contrast, the IC50 values of CM-II-sPLA2 against viruses that bud through the PM (Sindbis virus, influenza virus and Sendai virus) or trans-Golgi network (TGN) (herpes simplex virus) were >10,000 ng/ml. Moreover, the 50% cytotoxic (CC50) and haemolytic (HC50) concentrations of CM-II-sPLA2 were >10,000 ng/ml, implying that CM-II-sPLA2 did not significantly damage the PM. These results suggest that CM-II-sPLA2 and its derivatives are good candidates for the development of broad-spectrum antiviral drugs that target viral envelope lipid bilayers derived from the ER membrane.

Antiviral and virucidal activities of Duabanga grandiflora leaf extract against Pseudorabies virus in vitro

BACKGROUND

Duabanga grandiflora or known in Malaysia as Berembang Bukit, Megawasih, or Pedada Bukit, is a native plant of the Southeast Asian countries. In this study, the anti-viral properties of D. grandiflora were investigated.

METHODS

The D. grandiflora leaf extracts were obtained with ethyl acetate, hexane, and ethanol as solvents and labelled 37 leaf ethyl acetate (37 L EA), 37 leaf hexane (37 L H), 37 leaf ethanol (37 L ET), respectively. The cytotoxicity of the extracts on Vero cells were determined by the 3-(4,5-Diamethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay.

RESULTS

Among extracts, 37 L EA was most cytotoxic to Vero cells, followed by 37 L H and 37 L ET, with CC50 of 218, 833, and >1000 μg/mL, respectively. The cytopathic effect (CPE) and plaque reduction, inhibition, and virucidal assays and the selective index (SI) were employed to determine the effect of the extracts on infectivity and replication of pseudorabies virus (PrV) in Vero cells. The D. grandiflora leaf extracts showed dose-dependent antiviral activities, with higher activities at high doses. The 37 L ET and 37 L EA showed anti-viral effects through plaque formation and viral replication inhibitions, and virucidal property. The SI of the 37 L ET and 37 L EA by the viral replication inhibition assay was 8.3 and 1.9, respectively, and by the CPE reduction assay, 6.7 and 2.9, respectively.

CONCLUSION

Ethanol is the best solvent for the preparation of D. grandiflora leaf extract as an antiviral agent.