The foliar micromorphology and medIicinal phytochemicalpProperties of Heteropyxis Natalensis (Myrtaceae).

Abstract

The use of medicinal plants as a form of therapeutic healing is an ancient tradition in various regions of the world. As a result, there is a dire need to screen medicinal plants for their unrevealed pharmacological potential. The foliar micromorphology of plants enables researchers to investigate the synthesis and location of medicinal phytocompounds. Heteropyxis natalensis is a South African medicinal plant and is traditionally used in Venda and Zulu communities to treat several illnesses. This study aimed to characterise the foliar structures of H. natalensis leaves, locate the site of secondary metabolites, determine the phytochemical composition of the leaves, and investigate the antibacterial efficacies and silver nanoparticles (AgNPs) of the methanolic extract. Emergent, young and mature leaves were examined using various microscopy techniques which confirmed the presence of non-glandular trichomes as the main external appendages of the leaves. Micrographs also revealed internal secretory cavities and crystal idioblasts. Secretory cavities were observed accumulating amorphous secretions and histochemical tests detected alkaloids, phenolics, essential oils and lipids. Qualitative phytochemical analyses were conducted on hexane, chloroform and methanol leaf extracts, and detected phenolics, alkaloids, saponins, sterols and terpenes. Crude methanolic extract was further examined using gas chromatographymass spectrometry and identified several important bioactive compounds of pharmacological value. A “green approach” was used to synthesise AgNPs using the methanolic leaf extract. Characterisation studies identified spherical particles below 100 nm in size, as well as the functional groups responsible for the capping of silver ions (Ag+). The crude methanolic extract and AgNPs were screened for their antibacterial efficacy and showed inhibition of five pathogenic bacterial strains. The results obtained in this study revealed that the phytochemical compounds present in H. natalensis leaves justify the use of this species in traditional medicine.