Anti-herpes simplex and antioxidant value of selected medicinal plants cited for management of HIV conditions in Western Kenya

Abstract

Medicinal plant products are common medication therapy in traditional healing practices. However, the product plant species and their health value are often not scientifically authenticated. Given multiple challenges of unmet needs in care and management of HIV conditions, People living with HIV (PLWHIV) are prone to utilization of the plants with consequent risk of lack of expected benefits and at worst, fatality. The aim of this study was to identify plants used by PLWHIV in Hamuyundi and Mukhwa communities in Western Kenya and to determine cytotoxicity, anti-Herpes activity, antioxidant value and to phytochemical groups of selected plant species. The identification of plants was carried out by qualitative ethnobotanical survey, using Community Health Workers as key informants. Plant species were collected from the field and botanically identified at the University of Nairobi herbarium. By literature search, secondary metabolites and pharmacological activity reported in previous studies on the plants were identified. Water extract of eight selected medicinal plants were tested for cytotoxicity and anti-herpes activity using Vero cell and Herpes simplex type 1 (HSV-1). The effect of extract on cell metabolism of tetrazolium dye (MTT) was measured to determine cytotoxicity. The anti-herpes activity was determined by measuring metabolism of MTT by cells exposed to HSV-1 in presence of extracts. The antioxidant value was determined by measuring reduction of 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) by extracts of selected plant species. The extracts were then tested for the presence of flavonoids, terpenoids, alkaloids, saponins and phenols qualitative procedures. At Hamuyundi community, a total of 36 plant species from 26 families were identified while in Mukhwa, 29 species distributed in 17 families were identified. From literature, it was established that a third of plant species identified as medicinal in both Hamuyundi and Mukhwa have some of their pharmaceutical activity and or phytochemical contents identified. Except for Garcinia buchananii (Baker) (Bark) and Croton macrostachys (Hoechst) (Bark) that gave maximum nontoxic concentration (MNC) of 40 µg/mL each, all the other species; Tithonia diversifolia (Hemsl.) Gray (Roots), Schkuria piñata (Lam) O.Ktze (Leaves), Entada abyssinica (A. Rich) (bark), Vernonia adoensis Walp (roots), Plumeria alba L. (leaves), Caesalpinia decapetala (Roth. I. Alston) (root) gave MNC of 20 µg/mL and below. The extract concentration that was cytotoxic to 50% of the cells (CC50) of A. abyssinica, G. buchananii and C. macrostachys were above 500µg/mL while CC50 of C. decapetala (roots), V. adoensis (roots) T. diversifolia (roots), P. alba (leaves) and S. pinata (leaves) were 500, 470, 460, 120 and 90 µg/mL respectively. The best anti-herpes activity was obtained from G. buchanii (stem bark), giving an extract concentration inhibiting 50% of virus activity (IC50) at 20µg/mL) and C. decapetala (whole root) giving IC50 at 80µg/mL. Therapeutic index (TI) of G. buchanii was ˃ 25 and that of C. decapetala was ˃ 6. Garcinia buchananii extract was active against HSV-1 infection in mice at 500µg/mL, when compared with negative control by independent t-test, significantly delaying onset of symptoms (p = 0.006), progression of symptoms, (p= 0.005) and day of death (p =0.007). The most potent antioxidant activity was given by E. abyssinica, G. buchananii and C. decapetala, giving sample concentration reducing DPPH by 50% (Rsa50) of 20, 10 and 50µg/mL respectively. Major phytochemical groups detected in the selected plants were Alkaloids in S. pinata, terpenoids in E. abyssinica, flavonoids and phenols in G. buchananii. Results show that there is scientific basis for use of many plants in Hamuyundi and Mukhwa communities in Western Kenya. Further investigation is required to isolate and characterize compounds responsible for activity found in G. buchananii and C. decapetala