Analysis of triacylglycerols in leaves of citrus by HPLC

Lipids were extracted from leaves of cold-hardened and unhardened citrus plants and the crude triacylglycerol (TG) fraction of each sample was separated from other lipid components by silica gel column and thin layer chromatography (TLC). To determine TG levels and molecular species, the crude TG was subjected to High presure liquid chromatography (HPLC), 12 fractions collected and these fractions quantified by gas liquid chromatography (GLC). Levels of TG/g fresh leaf were 139 µg in unhardened sour orange, 2460 µg in cold-hardened sour orange and 672 µg in cold-hardened Valencia orange. Twenty-one molecular species were determined in the 36–46 equivalent carbon number range (ECN). Five of the TG species that contained linoleate accounted for over 60% of total TG in hardened sour orange and Valencia leaves. Hardened sour orange leaves contained 2–5 times more of these major TG species than hardened Valencia leaves. The increase in these TG species may relate to cold tolerance since sour orange seedlings are more cold hardy than Valencia budded on sour orange.