TITLE:
Toxicity and Antiviral Activities of Some Medicinal Plants Used by Traditional Medical Practitioners in Zimbabwe
AUTHORS:
Deniz Iklim Viol, Lameck Shoriwa Chagonda, Sylvester Rodgers Moyo, Ali Hikmet Mericli
KEYWORDS:
Medicinal Plants, Toxicity, Antiviral Activity, Herpes Simplex Virus-2, Zimbabwe
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.11,
August
10,
2016
ABSTRACT: Genital herpes, usually caused by Herpes
Simplex Virus type-2 (HSV-2), is the commonest sexually transmitted disease
especially amongst rural women in Southern Africa including Zimbabwe. This
predisposes them to HIV/AIDS infection, cancer and opportunistic infections (OIs).
Current antiviral treatments are often cytotoxic and/or ineffective. This
motivates active research to find alternative safer drugs or lead drugs from
traditional medicinal sources. Twenty six (26) methanol extracts from commonly
used and often endangered plant species (14) used by communities and
traditional medical practitioners for treating illnesses and sexually
transmitted diseases from 5-selected districts of Zimbabwe were investigated
for toxicity by Brine shrimp lethality test (BSLT) and by 50% Cytopathic effect
on VERO cultured cells. The extracts were also tested for antiviral activity
against Herpes Simplex Virus-2 (HSV-2) by the End Point Titration Technique
(EPTT) and Neutralisation Test (NT) on VERO cells. Results from the BSLTs
ranged 66.66 - 4304 μg/ml; 50% Cytopathic effect
from 19.53 - 312 μg/ml whilst the NT ID50 values ranged from 10.41 -
125 μg/ml. The antiviral EPTT reduction factor (RF) was 1 - 104 with 13 extracts showing RF ≥ 103. All the
plant extracts had moderate to high toxicity (LC50, 789 - 66 μg/ml)
in the BSLT. Six extracts had LC50 values greater than 1000 μg/ml.
All 26 extracts were cytotoxic with CC50 values 50 in vitro therapeutic indexes ≥ 3.7. Cassia abbreviata, Dichrostachys cinerea and Hypoxis hemerocallidea had therapeutic indexes (TI) 7.5 -
15.0. The more active plant extracts were from roots and root tubers. The
results confirm the rationale for the use of traditional medicinal plants by
traditional medical practitioners for treating various diseases and could bring
awareness for their better use and improve conservation. The results also
provide an opportunity to develop more efficacious drugs by isolating lead
compounds and determining their mode of action.