Phytochemical, elemental and biological studies of three Ficus species (Moraceae) found in KwaZulu-Natal, South Africa.

Abstract

Ficus (Moraceae), with over 800 species, is one of the understudied genera in modern pharmacognosy. Rural households depend on their fruits for food while other plant parts such as leaves and bark are utilised for medicinal purposes. Phytochemical analyses and biological activities of different plant parts, as well as the nutritional value of the edible fruits of many of the species are yet to be investigated. This study aimed at investigating three Ficus species (Ficus burtt-davyi, Ficus sur Forssk and Ficus sycomorous Linn) that produce edible fruits and are indigenous to KwaZulu-Natal, South Africa, as a source of secondary metabolites and essential dietary elements, due to their claimed medicinal and nutritional value. Plant material was subjected to chromatographic analyses and isolated compounds were identified using spectroscopic techniques and by comparison with previously reported data. Fruit and soil samples that were collected from sites within KwaZulu-Natal, were digested and analysed for macro, micro and toxic elements by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The phytochemical investigation of F. burtt-davyi revealed the bark to be rich in pentacyclic triterpenoids (lupeol and lupeol acetate) and the known antioxidant flavonoid ((+)-catechin) whilst the leaves were rich in sterols (β-sitosterol, campesterol, and stigmasterol). Both leaves and fruits also contained phaeophytin a, lutein and α-amyrin. This is the first phytochemical report on this species. The cytotoxic results indicated that lupeol and (+)-catechin, the most abundant bioactive compounds in the stem bark, were responsible for its synergistic cytotoxic effects against breast and colorectal adenocarcinoma cell lines. This study supports the use of this plant species as a substitute for antioxidant supplements and as an alternative medicine for oxidative stress related iv non-communicable chronic diseases in vulnerable communities. The phytochemical analysis of F. sur revealed two pharmacologically active triterpenoids (lupeol and sitosterol), one pheaophytin (pheaphytin a) and one flavonoid (epicatechin). The analytical results indicated that the fruits of F. burtt-davyi, F. sur and F. sycomorous are good sources of essential dietary elements and can contribute significantly (p < 0.05) to the recommended dietary allowances (RDAs) for most nutrients. The fruits of F. sur and F. burttdavyi are good dietary sources of Se and Mn, respectively. The concentrations of As, Cd, and Pb were below the instrument detection limits in all three figs indicating that the species do not tend to accumulate these toxic elements. Data from this study showed that metal interactions in soil influenced their availability, but uptake was to a greater extent controlled by the plant. Statistical analyses revealed synergistic relationships in the plants, thereby confirming that uptake of elements is controlled to meet metabolic needs. Overall, this study validates the ethnomedicinal use of these figs and reveals the nutritional and medicinal benefits of consuming the indigenous edible fruits. It also addressed the need for analytical information on the elemental concentrations in indigenous edible fruits consumed in South Africa.