Abstract

This study compared the chemical composition of the essential oils obtained by hydrodistillation of different tissues of Piper capense, Piper guineense, Piper nigrumand Piper umbellatum grown in Cameroon. The GC and GC/MS analysis showed qualitative and quantitative differences between these oils. Oils from the fruits were rich in a-pinene (5.6 - 12.3%) and b-pinene (6.7 - 59.3%). The other major constituents were sabinene (14.7%) for P. capense, limonene (15.8%) and b-caryophyllene (20.8%) for P. guineense. The oil from the fruits of P. nigrumcontained sabinene (11.2%), d-3-carene (18.5%), limonene (14.7%) and b-caryophyllene (12.8%) while that of P. umbellatum content linalool (14.4%) and(E)-nerolidol (10.0%) as major constituents. The essential oil obtained from the leaves of P. capense was largely composed of a-pinene (12.8%), β-pinene (50.1%) and b-caryophyllene (12.4%). The most abundant constituents identified in the oil from the leaves of P. guineense were limonene (10.3%) and germacrene B (25.1%) while that from P. nigrum was characterized by its high amount of a-selinene (16.5%) and β-selinene (14.6%). β-pinene (10.8%), β-caryophyllene (28.2%) and(E)-nerolidol (16.5%) were the quantitative important constituents of the essential oils from the leaves of P. umbellatum. The oils from the lianas of P. guineense was rich in (Z, E)-a-farnesene (28.7%), limonene (19.7%) and myristicine (10.9%), while those from P. nigrum contained d-3-carene (14.4%) and β-caryophyllene (36.0%). The oil from the stems of P. capense contained mostly a-pinene (14.3%) and β-pinene (61.4%). The distillation of those from P. umbellatum did not produce any essential oil. Oils from the three fruits showed variable contact toxicity againstSitophilus zeamais with P. guineense being more toxic (LD₅₀ = 10.0 ± 0.3 µl/g) thanP. capense (LD₅₀ = 16.1 ± 0.6 µl/g) and P. nigrum (LD₅₀ = 26.4 ± 1.5 µl/g). Poudrox (5%) used as a standard insecticide exhibited 100% mortality.

Key words: Piper capense L., P.guineense Schum. Et Thonn., P. nigrum L., P. umbellatum L, essential oils, a-pinene, b-pinene, b-caryophyllene, insecticidal,Sitophilus zeamais Motsch.