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 < 500 ug/ml of which 19 were more toxic CC50 < 100 ug/ml. Nine extracts had 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.
Highlights
Third world countries are often endowed with rich flora and fauna which are put to good use in their traditional medical practices
The HIV/AIDS virus still remain a threat to mankind and the current report presents the toxicity and antiviral properties of 14 plant species used in traditional medical practice which could have a bearing on the development of potential antiviral and anticancer drugs
The use of Traditional Medical Practitioners (TMPs) is often plagued with issues of safety and/or toxicity
Summary
Third world countries are often endowed with rich flora and fauna which are put to good use in their traditional medical practices. With over 55,000 registered TMPs in Zimbabwe alone, the protection of the 500 medicinal plants identified as playing a significant role in the traditional practice becomes a problem for conservationists [1]. The laboratory studies confirmed the rationale for their use in traditional medical practice in line with other studies elsewhere to evaluate TMs targeted at finding alternative safer drugs to treat modern illnesses and to overcome growing resistance to infective agents. The HIV/AIDS virus still remain a threat to mankind and the current report presents the toxicity and antiviral properties of 14 plant species used in traditional medical practice which could have a bearing on the development of potential antiviral and anticancer drugs. This report highlights some of the key findings of the preliminary laboratory studies on toxicity and antiviral activities in the pilot study [12]
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