HIV infection induces a wide array of immunologic alterations resulting in the progressive development of opportunistic infections and malignancy, which results in AIDS . It has been observed that perturbations in the antioxidant defense systems, and consequently redox imbalance, are present in many tissues of HIV-infected patients . Moreover, there is clear evidence that oxidative stress may contribute to several aspects of HIV disease, including viral replication, inflammatory response and decreased immune cell proliferation . Hence, the exogenous supply of antioxidants, as natural compounds that scavenge free radicals, might represent an important additional strategy for the treatment of HIV infection.
Plants contain a wide variety of free radical scavenging molecules, such as flavonoids, anthocyanins, cartenoids, dietary glutathionine, alkaloids, tannins, saponins, steroids, terpenoids and rotenoids which are rich in antioxidant activities . In South Africa, there is a rapid proliferation of the consumption of plant based decoctions by HIV infected people. Herbal preparations are cheap and simple; hence they remain a hope for the infected people who cannot access the government sponsored antiretroviral programmes .
In the Eastern Cape Province of South Africa, traditional healing practices often coexist with formalized and institutionalized medicine systems. Ethnobotanical surveys conducted in this region highlighted some plants used for the treatment of opportunistic fungal infections (OFIs) in HIV/AIDS such as the decoction of Alepidea amatymbica (Apiaceae) for aspergillosis, infusion of Pittosporum viridiflorum (Pittosporaceae) for cryptococcal meningitis, decoction of Artemisia afra (Asteraceae) for oesopharyngeal candidiasis, infusion of Carpobrotus edulis (Mesembyanthemaceae) for oral candidiasis, lotion of Aloe ferox (Liliaceae) for vaginal candidiasis, infusion of Arctotis arctotoides (Asteraceae) and lotion of Gasteria bicolor (Asphodelaceae) for dermatophytoses (Otang et al., manuscript accepted for publication).
The stem and leaves of Gasteria bicolor were examined ; three new dihydroanthracenones namely 3,4-dihydro-2,6,9-trihydroxy-8-methyl-1(2 H)-anthracenone (gasteriacenone A), 3,4-dihydro-2,4,9-trihydroxy-6-methoxy-8-methyl-1(2 H)-anthracenone (gasteriacenone B) and 3,4-dihydro-4,6,9-trihydroxy-7-carbomethoxy-8-methyl-1(2 H)-anthracenone (gasteriacenone C) were determined. Their structures were elucidated by spectroscopic methods including 2D NMR techniques. A literature survey revealed that several species of the genus Pittosporum have been studied for their secondary metabolites. Triterpenoids and saponins were isolated from P. tobira, P. undulatum, P. phylliraeoides, P. pentaurum, and P. viridiflorum [5–8]. Bioassay guided purification of the ethanolic extract of the bark of New Caledonian Pittosporum pancheri Brongn. and Gris (Pittosporaceae) led to the isolation and characterisation of two new farnesylmonoglycosides, pancherins A and B. The in vitro antifungal activity of G. bicolor and P. viridiflorum have been investigated against a panel of opportunistic fungi in HIV/AIDS in our previous study  and by other authors [7, 10].
Although the antioxidant and phytochemical properties for some of these plants have been investigated in different countries [11–15], there is a dearth of knowledge of such studies on G. bicolor and P. viridiflorum in South Africa. The aim of this study was therefore to analyse the phytochemical constituents and antioxidant potential of these plants. The antioxidant potential of the extracts, determined by DPPH, NO, and H2O2 and reducing power assays are designated by their IC50 (concentration required to attain 50% radical-scavenging effect) and compared with that of the standards (rutin, vitamin C, and Butylatedhydroxytoluene). The phytochemical and antioxidant screening of these plants is a prerequisite for verification and utilisation as new sources of herbal drugs .