Micropropagation and secondary metabolites in Agathosma betulina (Berg.)

Abstract

The global demand for medicinal plant products has increased in the last two decades leading to overexploitation and sometimes extinction of indigenous medicinal plants. Plant biotechnology offers an efficient approach to enhanced biosynthesis of essential and/or bioactive compounds in plants. This study was aimed at developing a micropropagation protocol for Agathosma betulina Berg. (Buchu), one of the most highly utilized aromatic medicinal plants in South Africa. The study also aimed to develop a technique that will enhance the biosynthesis of some bioactive compounds by manipulating the media composition. Seeds and nodal explants from Buchu were decontaminated, germinated and sub-cultured on Murashige and Skoog (1962) (MS) media adjusted with different concentrations of N6-Benzyladenine (BA), 1-naphthaleneacetic acid (NAA) and dichlorophenoxy acetic acid (2,4-D). Dried samples from in vitro cultures were extracted using dichloromethane and analyzed for phytochemical compositions using GC–MS. In vitro seed germination produced healthy seedlings that can be transplanted ex vitro. Significantly higher shoot proliferation was recorded in nodal explants grown in 1/2 strength MS supplemented with 2,4-D and a combination of NAA and BA. Phytochemical analysis revealed significantly higher amounts of limonene accumulated in callus compared to other plant parts. The most abundant phytochemicals were recorded in plants grown on media supplemented with NAA 2.7 μM; these include limonene, pulegone and isomenthone (68, 39 and 33 μg kg− 1 DW respectively). Biosynthesis of certain compounds in in vitro culture of Buchu was induced by plant growth regulator application compared to the control. The plants possess a number of pharmacological properties including anticancer, antimicrobial and antioxidant. These activities are linked to inherent phytochemical contents. Hence, the use of micropropagation techniques that will enhance the biosynthesis of some bioactive compounds in Buchu will be an efficient means to meet the high demands for this plant.