Leaf Pigments and Their Derivatives in Tobacco (Nicotiana tabacumL.) in Relation to Curing Methods and Leaf Position

Abstract

Present study was undertaken to assess the effect of curing methods on leaf pigments and their derivatives in air cured Oriental and Flue-cured Virginia (FCV) tobacco in relation to leaf position. The pigments identified in cured tobacco leaf included chlorophylls, carotenoids, pheophytin, chlorophyllide, protoporphyrin and magnesium protoporphyrin. Total chlorophyll (Tchl) content varied from 148 to 231 μg g−1 among the leaf positions and curing methods. Tchl content was significantly higher in Oriental tobacco compared to FCV tobacco and bottom position leaf of Oriental tobacco showed significantly higher levels of Tchl compared to the middle and top position leaves. Carotenoid content varied from 197 to 456 μg g−1 among the leaf positions and tobacco types. FCV tobacco showed significantly higher levels of carotenoids, more polar carotenoids (MPC) and less polar carotenoids (LPC) than Oriental tobacco. The carotenoid content was similar among the leaf positions. Pheophytin a (Phe a) content was similar in Oriental and FCV tobacco while pheophytin b (Phe b) was significantly higher in Oriental tobacco. FCV tobacco contained significantly lower levels of protoporphyrin and magnesium protoporphyrin than Oriental tobacco. Chlorophyllide a (Chlide a) content varied between 1.73 to 3.4 μ mole g−1 among the leaf positions and tobacco types and its content decreased significantly in top leaves. Top position leaf of Oriental tobacco showed significantly lower levels of Chilide a when compared to bottom position leaf of both tobacco types. Chlorophyllide b (Chlide b) content also showed same trends as Chlide a but its content was significantly lower in FCV than in Oriental tobacco. Pheophorbide compounds were not detected in both types of tobacco. The results revealed that the end product of the chlorophyll degradation may be chlide in tobacco and the degradation of chlorophyll pigments due to curing was greater in FCV tobacco when compared to Oriental tobacco.