DOI: 10.14457/tu.the.2021.796
title: Antiviral activity of Benchalokawichian, Prasachandaeng and its plant components extracts against herpes simplex virus

description: Herpes simplex virus (HSV) causes severe illness, including neurological disease. HSV consists of two types: HSV-1 and HSV-2, associated with oral-facial and oral-genital infection. However, HSV-2 infection is the commonest cause of herpes. Antibiotics are used to treat herpes, but antibiotic misuse can promote drug resistance to herpes simplex virus. For this reason, herbal medicines may be investigated to provide new antiviral agents. Benchalokawichian (BLW) and Prasachandaeng (PJD) are included on Thailand's National List of Essential Drugs. They are used to treat fever and lower body temperature. In addition, folk healers use them to treat skin diseases. BLW consists of five bases: Capparis micracantha, Tiliacora triandra, Harrisonia perforate, Clerodendrum indicum, and Ficus racemose. Prasachandaeng consists of twelve plants: Bouea macrophylla Griff, Caesalpinia sappan, Citrus aurantifolia (Christm)Swingle, Dracaena cochinchinensis (Lour.) S.C. Chen, Heliciopsis terminalis Kurz )Sleumer), Jasminum sambac L.) Aiton), Kaempferia galanga L, Ligusticum Chuanxiang Hort, Mammea siamensis T.Andersin, Mesua ferrea L, Myristica fragrans Hout, and Nelumbo nucifera Gaertn. Inhibition effect of BLW and PJD against HSV-2 has not yet been investigated for HSV. Therefore, this study aimed to examine the antiviral activity of BLW, PJD, and their plant component extracts against HSV-2. First, cytotoxic activity of all extracts on Vero cells was tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay at two hours and after three days. The results found that all samples showed no cytotoxicity for antiviral activity by plaque reduction assay for pre-incubation assay, pre-treatment assay, and pre-treatment assay. Ethanolic and aqueous BLW extracts revealed that Vero cell had non-cytotoxicity at 100 µg/mL after two hours and three days of incubation. BLW extracts were pre-incubated with HSV-2 for two hours before infection. After pre-incubation, the inhibition effect of BLW extracts against HSV-2 was below 50% at 100 µg/mL. Similarly, BLW extracts showed less effect against HSV-2 with pre-treatment assay and post-treatment assay. Ethanolic extract of PJD showed no Vero cell toxicity at 100 µg/mL after two hours of incubation. However, it was toxic to Vero cells at 100 µg/mL after three days of incubation. An inhibitory effect could be observed when the ethanolic extract of PJD was incubated with HSV-2 before infection to Vero cells (IC50 = 24.46±6.05 µg/mL). For pre-treatment assay and post-treatment assay, the inhibition percentage of ethanolic extract of PJD against HSV-2 was under 50% at the highest concentration, with no toxic effect on cells. Ethanolic extract of D. cochinensis, the main ingredient of PJD, showed potent anti-HSV-2 with IC50 of 37.23±4.15 µg/mL. C. sappan and K. galangal, plant ingredients of PJD, observed by pre-incubation assay. C. sappan had the highest antiviral activity against HSV-2 with an IC50 value of 1.91±0.13 µg/mL, while K. galangal did not inhibit HSV-2. Brazilin and Ethyl-p-methoxycinnamate (EPMC) were found in PJD extract to have an inhibitory effect against HSV-2 with IC50 values of 4.28±1.64 and &gt;100 µg/mL in the pre-incubation process.Aqueous extract of PJD revealed no anti-HSV-2. However, after hydrolysis, anti-HSV-2 activity existed with IC50 value of 28.03±6.44 µg/mL. To compare the chemical fingerprint between acid hydrolysis extract and PJD aqueous extract, thin-layer chromatography (TLC) was used to monitor the PJD chemical compound. Many different chemical compounds were made between PJD acid hydrolysis and aqueous extraction. The acid hydrolysis process may cause chemical changes in the aqueous extract. These findings suggest that PJD ethanolic and acid hydrolysis extracts eliminated HSV-2 directly. Its plant components, including D. cochinensis, C. sappan, and brazilin, a pure compound of PJD, were effective against HSV-2. However, PJD was suitable for development as an external drug due to its direct effect on herpes viruses.