Secondary Metabolites Composition and Their Histochemical Localization in the Fruit of <i>Piper malgassicum</i> Papini, Palchetti, Gori and Rota Nodari (Piperaceae)

The anatomy, histochemistry, and secondary metabolite composition were investigated on the drupes of Piper malgassicum, one of the components of the spice voatsiperifery pepper. The high amount of piperine recorded with high-performance liquid chromatography with photodiode-array detection analysis was localized with histochemistry mainly along the fruit mesocarp in idioblasts, since they were positive to alkaloids (Wagner reaction). The fruit was analyzed at different stages of maturation. β-carotene reached the highest concentration when the drupe was at an intermediate stage of maturity (orange color) and maintained the same concentration also at full maturation (red color). The terpenes fraction present in higher amounts decreased with fruit ripening (as also piperine). Terpenes are presumably at their maximal concentration at the middle stage of fruit ripening to avoid damage to the pericarp by fungi and bacteria, while piperine would avoid feeding by animals. The reduction in concentration of these two components is linked to the seed dispersal stage after full fruit maturation. Both the most abundant terpenes, α-phellandrene and linalool, show antimicrobial properties. These compounds are also known for anti-inflammatory properties in vivo and in vitro, and hence, this plant may have medicinal properties. Since the total amount of terpenes is highest at an intermediate stage of fruit maturation, the optimal timing of collection would be prior to full maturation.