橘皮色素的分析

Analysis on Pigments in the Exocarp of Orange Fruit

本研究檢測橘皮後熟階段葉綠素和類胡蘿蔔素，及三種葉綠素生合成途徑的中間代謝物——protoporphyrin IX (PPIX)，magnesium protoporphyrin IX (MGPP)和protochlorophyllide (Pchlide)，的含量變化。當葉綠素含量下降12倍，類胡蘿蔔素都保持相似的含量。同期間，葉綠素a∕b比，類胡蘿蔔素∕葉綠素比和Pchlide∕葉綠素比分別自2.51，0.22和1.00改變為4.42，2.74和0.07。因此，類胡蘿蔔素的缺失並不直接伴隨著葉綠素的缺失；葉綠素b的崩解比葉綠素a快速；PPIX的崩解比MGPP和Pchlide緩慢；在後熟的最後階段，殘餘的Pchlide似更容易轉化為葉綠素而非崩解。

We examined the chlorophyll (Chl) and carotenoid contents, and the three Intermediates (protoporphyrin IX(PPIX), magnesium protoporphyrin IX (MGPP) and Protochlorophyllide (Pchlide)) of Chl biosynthetic pathway in the exocarp of orange fruit during its late ripening stage. While Chi content declines by 12 folds, carotenoid content always remains similar level. Meanwhile, the ratios of Chl a/b, carotenoid/Chl and Pchlide/Chl alter from 1.51 to 4.42, from 0.22 to 2.74 and from 1.00 to 0.07, respectively. It is, therefore, concluded: (a) the deficiency of carotenoid is not directly accompanied by the deficiency of Chl; (b) the degradation rate of Chl b is faster than that of Chl a; (c) the degradation rate of PPIX is slower than that of MGPP and Pchlide; and (d) as ripening takes place, the residual Pchlide is more easily forwarded to Chl.