Phytochemical, elemental and biological studies of three Ficus species (Moraceae) found in KwaZulu-Natal, South Africa.
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Date
2017
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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
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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.
Description
Doctor of Philosophy in Chemistry. University of KwaZulu-Natal, Durban 2017.