Variations in the quassin and neoquassin content in Quassia amara (Simaroubaceae) in Costa Rica: Ecological and management implications

Because of the quassinoids present in its tissues, the tropical shrub, Quas sia amara (Simaroubaceae) is used to make medicinal extracts and insecticid es. By means of high performance liquid chromatography, the levels of quass ins and neoquassins were measured (0.28%, 0.20%, 0.16%, and 0.14% in branch es with diameters of > 4.5 cm, 3.0 - 4.5 cm, 1.5 - 3.0 cm, < 1.5 cm respect ively). Regression models were used to evaluate biomass and quassinoid quan tities at 4 pruning heights (0, 30, 50 and 100 cm) considering the shrubs' height and diameter (30 and 10 cm from the ground). It was found to be bett er to cut thick shafts and to prune low. The quassin content was not significantly different in populations from 5 c limatic regions in Costa Rica, but the neoquassin content did vary between 0.09% and 0.17%, and was higher in individuals found in very humid forests. The hypothesis proposed here is that quassinoids accumulate in the shrub's xylem as it grows, and that more chemicals are produced under less favoura ble growing conditions, such as those found in humid and very humid forests where the available light is limited. The distribution study of the species in Costa Rica shows denser population s in areas with less than 450 m above sea level with unlimited water supply , good drainage and high light levels. In areas with less than 2500 mm of a nnual precipitation, the shrub is found only in riparian forests. In humid and very humid forests (with up to 5500 mm of precipitation) the shrub is m ore prevalent in areas with higher light levels. A plan for the sustainable use of the species in a natural population in Costa Rica is discussed.