In vitro propagation of spilanthes mauritiana dc., an endangered medicinal herb, through axillary bud cultures

Abstract

Spilanthes mauritiana DC., a monogeneric-endangered herb belonging to the Compositae family, is a native of Eastern Africa and is used in the local pharmacoepia to cure infections of the throat and mouth (Watt and Brayer-Brandwijk, 1962), and as remedy for stomach ache and diarrhea (Kokwaro, 1976). Kamba tribes in Kenya chew the flower of S. mauritiana for the relief of toothache and the treatment of pyorrhea (Watt and Brayer- Brandwijk, 1962), and an infusion of the herb is used as a febrifuge (Dalziel, 1937). In the Cameroons the plant is used as a snake-bite remedy and in the treatment of articular rheumatism (Dalziel, 1937). In India the plant has been used as a remedy for kidney stones, and bladder and kidney infections (Dragendorff, 1898). In contrast, the flowering head is reported to produce stupefaction of fish and to be used as fish poison (Dragendorff, 1898). So far the only isolated active principle in S. mauritiana is an antiseptic alkaloid, spilanthol, present at a concentration of as much as 1.25% in the flowers (Watt and Brayer-Brandwijk, 1962). Spilanthol is effective against blood parasites at extremely low concentrations, and indeed is a poison to most invertebrates, while remaining harmless to the majority of vertebrates (Watt and Brayer-Brandwijk, 1962). Researchers have shown preliminary antimicrobial activity in the crude extract from roots and flower heads of S. mauritiana (Fabry et al., 1996, 1998). One of the essential requirements for the successful application of plant propagation technology to agriculture is the capacity to regenerate elite plantlets. During the past decade, the demand for elite plantlets has undergone a steep rise. To meet this ever-growing commercial need, the realization of in vitro production of a large number of clonal plants with improved characteristics has become necessary. Additionally, clonal propagation of elite plantlets still remains the only way to conserve endangered plant species. The accelerating loss of plant species as a result of destruction of their tropical habitat has yielded a revival of interest in the propagation of endangered plants (Moncousin, 1991). Given that clonal propagation also preserves the genetic stability of the progeny, collections are important ex situ germplasm reservoirs. In order to study and characterize the bioactive compounds in S. mauritiana, a constant source of this plant is needed, yet the natural habitat of the plant is under severe pressure and is constantly shrinking. The present communication reports for the first time the clonal propagation of S. mauritiana through axillary bud cultures.