Chlorophyll Catabolism in Ethylene-treated Citrus unshiu Fruits

Abstract

Changes in the levels of chlorophylls (Chls) and their derivatives were determined to clarify the Chl metabolic pathway in ethylene-treated satsuma mandarin (Citrus unshiu Marc. cv. Nichinan No. 1) fruits held in the dark. The fruits were treated with or without 200 ppm ethylene for 16 hr in a 20-1 desiccator at 25°C in darkness. After the treatment, the fruits were further stored in fresh air at 25°C in the dark for 72 hr. Chl pigments in the peel monitored with HPLC revealed that they remained unchanged during ethylene treatment. After 40 hours of treatment, a decrease occurred in the levels of Chl a, Chl b, and pheophytin a. With or without ethylene, low levels of chlorophyllide a (Chlide a), 132-Hydroxy (HO) Chl a, pheophorbide a (Phed a), and pyropheophorbide a (Pyrophed a) were eluted as Chl a derivatives. Chlide b and its derivatives could not be detected. The ratio of Chl a to b in the ethylene-treated fruits increased significantly with the advance of degreening. The ethylene-induced Chl metabolic process in Citrus unshiu fruits is discussed.