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Debprasad Chattopadhyay et al.
Table 2. Continued
Phenolics and polyphenols The simplest bioactive polyphenols with a single substituted phenolic ring belongs to phenylpropane that are in the highest oxidation state and have wide range of antiviral activities. The aqueous extract of Geranium sanguineum L. aerial roots containing polyphenolic complex catechins and condensed tannins was reported to inhibit both HSV-1 and HSV-2 (EC50 3.6-6.2 µg/ml) and at MIC90 (120µg/ml) it strongly inactivate HSV-1Kupka strain in plaque reduction assay, and delayed the development of herpetic vesicles in guinea pig [Serkedjieva & Ivancheva, 1999]. Propolis, a crude extract of the balsam of various trees inhibits acyclovir-resistant HSV-1 and VZV due to the synergistic action of a mixture of terpenoids, flavonoids, benzoic acids esters, and phenolic acid esters [Huleihel & Isanu, 2002]. Interestingly the anticancer, antiinflammatory and immunomodulating agent caffeic acid phenethyl ester (CAPE), an active component of propolis from honeybee hives inhibit 70% of plaque formation in HSV at 10M dose, while at higher concentration it inhibits RNA, protein synthesis and proliferation of HSV [Huleihel & Isanu, 2002]. The aqueous extract of Plantago major L., a popular medicine of Ayurvedic, traditional Chinese medicine (TCM) and Chakma Talika Chikitsa of Bangladesh, used for treating ailments from cold to viral hepatitis, showed anti-HSV activity. Interestingly the isolated caffeic acid, chlorogenic acid and rosmarinic acid of P. major exhibited strongest activity against both HSV-1 (EC50 15.3µg/ml) and HSV-2 (EC50 87.3µg/m) [Chiang et al., 2002]. The SAR studies revealed that the site(s) and number of -OH groups on phenols are responsible for their antiviral activity. The Myrica rubra barks containing prodelphinidin-di-O-gallate inhibits HSV-2 attachment and penetration, and reduces viral infectivity by affecting the late stage of infection [Cheng et al., 2003]. Similarly Homalium cochinchinensis root bark containing cochinolide B, tremulacin and tremuloidin, inhibit HSV-1