Seed germination and medicinal properties of Alepidea species.

Abstract

The rhizomes of Alepidea amatymbica and Alepidea natalensis are used for medicinal purposes. Because of the increase in demand for these plants the species is becoming scarce. As the seed biology of neither species is well defined, conditions as well as treatments required for optimum germination and vigour were studied. Seeds were exposed to various physical factors such as varying light and temperature conditions and cold stratification, sowing depth and seed storage. The effects of smoke-water, butenolide (3-methyl-2H-furo [2, 3-c] pyran-2-one) a novel smoke compound and chemical substances (gibberellins, kinetin and KNO3) were also tested in order to improve seed germination. Alepidea amatymbica and A. natalensis achieved the highest seed germination (72.5% and 80%, respectively) at 25 °C under a 16 h photoperiod with a mean germination time (MGT) of 18 and 12 days, respectively. Phytochrome studies showed that A. natalensis requires light for germination. Cold stratification (5 °C) for 14-28 days significantly improved the percentage germination of both species (> 90%) compared to non-stratified seeds (control) at 25 °C under a 16 h photoperiod. Sowing A. amatymbica and A. natalensis seeds at a depth of 0.5 cm resulted in higher percentage germination compared to 2.5 cm. The highest emergence rate for A. amatymbica was 40% at a sowing depth of 0.5 cm and the lowest emergence rate was 3% at 2.5 cm. Six months storage of A. natalensis seeds at room temperature (25 ± 2 °C) showed maximum germination (99%) with a MGT of 9 days. Smoke-water treatment of A. amatymbica seeds significantly enhanced germination from 72% to 91%. Smoke and butenolide at 10 °C and 25 °C promoted germination of A. natalensis seeds in a 16 h photoperiod. Smokewater application significantly improved both germination and seedling vigour of A. natalensis. GA3 (10-8 M) was the best treatment for achieving maximum percentage germination of A. natalensis seeds. Antibacterial (two Gram-positive bacteria: Bacillus subtilis, Staphylococcus aureus and two Gram-negative bacteria: Escherichia coli, Klebsiella pneumoniae), antifungal (Candida albicans), anti-inflammatory (COX-1 and -2) and genotoxicity tests (Ames test) were carried out on petroleum ether (PE), dichloromethane (DCM), 80% ethanol (EtOH) and water extracts of the two Alepidea species. Water extracts of A. natalensis rhizomes exhibited high activity (MIC values of 0.78 mg/ml) against the four bacterial strains. High activity was also observed in the PE and DCM leaf extracts of the same plant against the Gram-positive bacteria. The PE and DCM extracts of A. amatymbica rhizomes exhibited the best activity (MIC values of 0.39 mg/ml) against Bacillus subtilis. The rest of the extracts showed low activity (MIC values >1 mg/ml). All the extracts showed activity against Candida albicans, with A. natalensis leaf extracts exhibiting the highest antifungal activity with MIC values of 0.88, 0.20 and 0.78 mg/ml for PE, DCM and EtOH, respectively. EtOH extracts had inhibition less than 40% for both A. natalensis and A. amatymbica. All the PE extracts showed higher inhibitory activity for COX-2 than for COX-1. PE and DCM extracts had percentage inhibitions above 70% in both COX-1 and COX-2 assays. The Ames test for genotoxicity revealed that none of the plant extracts were genotoxic to the Salmonella TA98 tester strain.