Comparative essential oils composition and insecticidal effect of different tissues of Piper capense L., Piper guineense Schum. et Thonn., Piper nigrum L. and Piper umbellatum L. grown in Cameroon
AbstractThis study compared the chemical composition of the essential oils obtained by hydrodistillation of different tissues of Piper capense, Piper guineense, Piper nigrum and 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. nigrum contained 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%), -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 -selinene (14.6%). -pinene (10.8%), -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 -caryophyllene
(36.0%). The oil from the stems of P. capense contained mostly a-pinene (14.3%) and -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 against Sitophilus zeamais with P. guineense being more toxic (LD50 =10.0 ± 0.3 ìl/g) than P. capense (LD50 = 16.1 ± 0.6 ìl/g) and P. nigrum (LD50 = 26.4 ± 1.5 ìl/g). Poudrox (5%) used as a standard insecticide exhibited 100% mortality.