Leaf alkaloid contents of Tabernaemontana pachysiphon as influenced by endogenous and environmental factors in the natural habitat

Indole alkaloid contents were investigated in leaves of Tabernaemontana pachysiphon (Apocynaceae) trees in the natural habitat, Shimba Hills National Reserve, Kenya. The contents of the major alkaloids apparicine, tubotaiwine, tubotaiwine- N-oxide, and isovoacangine varied with site, leaf age, leaf growth form, position in the crown, and plant age. Alkaloid contents were highest in young leaves. Trees bearing aberrant small dwarf-leaves showed similar alkaloid patterns as young leaves from healthy trees. At single trees, the contents were found to increase from the top to the bottom of the crown. Tree age had little influence on leaf alkaloid contents. In even aged leaves of trees from different forest sites, alkaloid contents were highest at the site with highest soil cation exchange capacity (CEC) and base saturation.