Phytochemical, elemental and biotechnological study of cryptocarya latifolia, an indigenous medicinal plant of South Africa.

Abstract

Cryptocarya latifolia (Lauraceae) is an indigenous South African plant used in ethnomedicinal practices. Traditional healers in KwaZulu-Natal, South Africa are extensively using the bark of C. latifolia as a substitute for Ocotea bullata, resulting in the decline of existing populations and also causing its conservation status to come under scrutiny. If no conservation efforts are instigated, the depletion and extinction of this species in the natural habitat is highly probable. Therefore, in this study, a phytochemical investigation of the leaves and fruits of C. latifolia was performed to determine their suitability, as a replacement for the bark, for medicinal use. From the leaves, a new compound, 5-hexyltetrahydro-2H-pyran-2-one (4) was isolated together with known compounds, quercetin-3-O-rhamnoside (1), β-sitosterol (2), copaene (3) and nerolidol (5). In addition, some important monoterpenoids, diterpenoids, sesquiterpenoids and essential oils were isolated and identified using gas chromatography-mass spectrometry (GC-MS). Quercetin-3-O-rhamnoside (1) and β-sitosterol (2) were also isolated from the edible fruits. Anti-oxidant activity of the isolated compounds using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging assay indicated good anti-oxidant activity of all compounds, except β-sitosterol (2), compared to ascorbic acid. The results reveal that the leaves and fruits can be used, instead of the bark, as a source of antioxidants. The analytical study conducted on the fruits of C. latifolia indicated that they are a good source of important dietary elements and may contribute significantly to the diet. The elements were found to be in increasing order of Pb <Cr < Se < Ni < Cu < Zn < Mn < Fe< Mg< Ca. Consumption of the edible fruits of C. latifolia could be beneficial to the rural populace and other vulnerable communities. In this study, an evaluation of decontamination, bud break, in vitro and ex vitro rooting in C. latifolia was also performed. Different types, combinations and concentrations of sterilants, fungicides and antibiotics were tested for the establishment of contaminant-free cultures. The most effective decontamination viii regime which resulted in 94% contaminant-free explants included the use of 70% ethanol, 1.75% sodium hypochlorite, Tween20®, Ampicillin®, Celest®, Heritage® and autoclaved distilled water at varying combinations, concentrations and time exposures. Thereafter, explants were grown in culture tubes containing Murashige and Skoog (MS) nutrient medium supplemented with various concentrations and combinations of cytokinin (benzylaminopurine - BAP) and auxin (naphthaleneacetic acid - NAA) to stimulate bud break. The treatment containing BAP:NAA at 1.0:0.01 mg L-1 resulted in the highest percentage of explants forming shoots (96%). This treatment also resulted in the longest shoot length (8.06 mm). The bud break protocol established can be used to produce C. latifolia shoots for medicinal or conservation purposes.