In vitro propagation and antibacterial activity in Cotyledon orbiculata: a valuable medicinal plant

Abstract

An effective in vitro propagation system via organogenesis was developed for Cotyledon orbiculata, a valuable medicinal plant. Plant regeneration and morphogenesis in vitro of C. orbiculata was initiated from leaf explants using various concentrations and combinations of plant growth regulators (PGRs). The highest number of regenerated shoots (20.0 ± 1.64) and shoot length (2.36 ± 0.27 cm) per explant was obtained on Murashige and Skoog (MS) medium supplemented with a combination of 5 µM thidiazuron and 2.0 μM benzyladenine. The regenerated shoots were elongated (6.47 ± 1.02 cm) when transferred to half-strength MS medium. Elongated shoots rooted (39.60 ± 1.27 per shoot) best in a half-strength MS medium containing 10 μM indole-3-butyric acid. Plantlets were successfully acclimatized (100 %) in a vermiculite-soil mixture (1:1 v/v) in the greenhouse. Rooting was also achieved ex vitro during acclimatization in a vermiculite-soil mixture (1:1 v/v) in the greenhouse with good plant growth. Different tissue types from in vitro culture (callus, shoots and plantlets) and leaves from ex vitro plants exhibited antibacterial activity [minimum inhibitory concentration (MIC) from 0.098 to 0.78 mg ml−1] against both Gram-positive and Gram-negative bacteria. In vitro and ex vitro developed plant tissues showed antibacterial activity (MIC of 0.195–0.78 mg ml−1) specifically against Klebsiella pneumoniae. Despite this, generally the leaf of ex vitro plants gave good activity (MIC of 0.195–0.78 mg ml−1) against both Gram-positive and Gram-negative bacteria. The present study indicated that tissue-culture-derived calli, shoots and plantlets, and ex vitro acclimatized leaves influenced therapeutic potential by the PGRs treatment used in the tissue culture system. The in vitro regenerated plants and its tissues of C. orbiculata using this protocol can be utilized as therapeutic agents for traditional medicine and for ex situ conservation.