Chemistry of the Australian Gymnosperms. Part IX. The Leaf Oils of the Australian Members of the Genus Callitris (Cupressaceae)

Abstract The leaf oils of the 18 species and four subspecies of the genus Callitris endemic to Australia have been investigated by a combination of GC and GC/MS. All taxa produced oils in poor to moderate yields. Callitris baileyi produced a leaf oil in which α-pinene and limonene together, contributed the majority of the oil, while in Callitris canescens methyl citronellate also made significant contributions to the oil. In C. columellaris, limonene was the principal component, contributing up to 78% of the oil. Callitris drummondii gave a leaf oil which showed two chemical varieties. The samples from Western Australia contained large amounts of α-pinene (67–69%), while the sample from South Australia contained limonene (10.9%), bornyl acetate (24.2%) and geranyl acetate (14.9%) as significant components. In C. endlicheri the main components were limonene, α-pinene and bornyl acetate. Limonene and α-pinene were the principal components of the leaf oil of C. glaucophylla. Callitris gracilis ssp. gracilis gave an oil in which the principal components were α-pinene, myrcene and limonene, while in ssp. murrayensis a-pinene was the principal component. α-Pinene and limonene were the principal components of C. intratropica and C. macleayana. Callitris muelleri was found in two chemical forms, one monoterpenoid and one sesquiterpenoid, with either a-pinene or spathulenol being the principal component. In C. oblonga, which consists of three subspecies, α-pinene was the main component. In C. preissii the major components were α-pinene, myrcene, limonene and bornyl acetate. Callitris rhomboidea was distinguished from the vast majority of other Callitris species by containing significant amounts of neryl acetate, geranyl acetate and citronellyl acetate. Callitris roei contained significant amounts of sesquiterpenes in its leaf oil, with (E)-nerolidol being the principal component. In C. tuberculata α-pinene and limonene were the major components. α-Pinene, limonene and camphor were the major components in the leaf oil of C. verrucosa, while in Callitris sp. (Emerald Falls PI. Forster +PIF26357) α-pinene and limonene were the principal components with significant amounts of α-fenchyl acetate. The leaf oil of the putative introgressed populations of C. columellaris—C. verrucosa had α-pinene (25–46%), myrcene (9–19%), limonene (14–24%), α-fenchyl acetate (8–13%) and bornyl acetate (4–13%) as the most significant components. The oil does provide similarities to the oils of both putative parent species in that it contains camphor (1–3%), which is characteristic of C. verrucosa and bornyl acetate (2–13%) characteristic of C. glaucophylla.