Description
Title: Terpenes from Callitris and Widdringtonia are New Labdanes with Antimicrobial and Acaricidal Activity (Cupressaceae)
Abstract: Despite the ethnobotanical reports of Callitris and Widdringtonia demonstrating antimicrobial and acaricidal effects, the diterpene acids from Widdringtonia have never been described and no comparison to the Australian clade sister genus Callitris has ever been made. Widdringtonia wallichii (syn. W. cedarbergensis), a critically endangered South African Clanwilliam cedar found in the Cederberg Mountains, was once prized for its long-lasting fragrant timbers and an essential oil that has an aroma similar to more well-known Mediterranean cedars and is primarily composed of widdrol, cedrol, and thujopsene. Two additional “cedars” known as W. nodiflora and W. schwarzii are found in South Africa, but their chemical similarity to W. wallichii has not yet been examined. Similar to Widdringtonia, Callitris was once prized for its termite-resistant woods and an essential oil that was primarily guaiol but also somewhat earthy. The present study shows that the essential oils were comparable in all three species of Widdringtonia, and two well-known non-volatile diterpene acids were found in leaves: the pimaradiene sandaracopimaric acid (1) and the labdane Z-communic acid (2) with a lower yield of the E-isomer (3). Additionally, the structures of five new antimicrobial labdanes were assigned to the leaves of the three species: 12-hydroxy-8R,17-epoxy-isocommunic acid, 8S-formyl-isocommunic acid, 8R,17-epoxy-isocommunic acid, 8R-17R-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy-epoxy (8). From its leaves, the Australian species of Callitris columellaris (also known as C. glaucophylla) also produced the acids 1, its isomer isopimaric acid, pisiferal (9), and pisiferic acid (10). The only major diterpene produced by Callitris endlicheri (Parl.) F.M.Bailey was isoozic acid (11). Spathulenol, guaiol, pisiferic acid, and diterpenes 4-6 all exhibited antimicrobial and acaricidal activity.
Keywords: Widdringtonia; Callitris; diterpene; cedar; essential oil; antimicrobial; NMR
Paper Quality: SCOPUS / Web of Science Level Research Paper
Subject: Antibiotics
Writer Experience: 20+ Years
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