In vitro evaluation of the antiviral activity of extracts from the lichen Parmelia perlata (L.) Ach. against three RNA viruses

Charles O Esimone,David O Olaleye,Dominic O Abonyi,Emmanuel C Ibezim,Georgina N Odaibo,Kenneth C Ofokansi,Michael U Adikwu

doi:10.3855/jidc.370

Abstract

Substances extracted from lichens have previously been reported to possess antimicrobial activities against various groups of bacteria, fungi and viruses. Due to the high abundance of Parmelia perlata in the Eastern parts of Nigeria, we decided to explore whether it possesses antiviral activity against some common animal and human viruses. The dried and powdered lichen was extracted with acetone, water and 4% (v/v) NaOH (to yield a crude polysaccharide fraction) using standard methods. The cytotoxicity of the extracts was investigated on HEP-2, Vero and L20 cell lines. The antiviral properties were determined against yellow fever, poliomyelitis and infectious bursal disease virus of chickens using the end-point cytopathic effect assay. Phytochemical evaluations of the extracts were also carried out. Phytochemical tests showed the presence of flavonoids, saponins, tannins, glycosides, steroidal aglycone, carbohydrates and also the presence, in trace amounts, of some oligodynamic elements. Cytotoxicity tests revealed that while L20 was susceptible to the extracts at a concentration of 50 microg/ml, the extracts were generally toxic to the cell lines at concentrations above 500 microg/ml. The order of sensitivity of the cell lines was L20 > HEP-2 > Vero. The water and acetone extracts showed no activity against the viruses when tested at concentrations below the cytotoxic level while the crude polysaccharide fraction showed activity against yellow fever virus with an IC50 of 15 microg/ml. The time of addition of the test extracts to the infected cells did not have significant effect on cytopathic effect inhibition. The results showed that the crude polysaccharide fraction from Parmelia perlata possesses specific antiviral activity against yellow fever virus. It is postulated that a major mechanism of inhibition of yellow fever infection by the crude polysaccharide fraction of the lichen could be by attack on the viral envelope.

Highlights

There are fewer substances available for the treatment of viral infections when compared with the large amount of available antibiotics for the treatment of bacterial infections
The potent activity of crude polysaccharide fraction (CPF) against the yellow fever virus (IC50 of 15 μg/ml) is plausible, especially considering that a previous report shows a major limitation to the detection of antiviral effects of compounds in in vitro assays is the extremely low concentration of extracts tolerated by cells in the artificial systems [2]
Cohen et al [9] isolated anthraquinones, bianthrones and hyperacin derivatives from lichens whose antiviral activities were positively correlated with increasing substitution of chlorine in the anthraquinone structure

Summary

Introduction

There are fewer substances available for the treatment of viral infections when compared with the large amount of available antibiotics for the treatment of bacterial infections. Parmelia perlata grows on trees and rocks especially in the West of Britain and in the tropics [11]. It forms large light-grey patches with rounded lobes, which often have black hairs at the edges. There has been a renewed interest in the search for antivirals from the plant kingdom [4,12]. This interest provided the necessary stimulus to undertake this present study, which aims to evaluate the in vitro cytotoxic and antiviral properties of extracts from the lichen P. perlata

Materials and Methods

Results

Discussion