Antibacterial Constituents of The Australian Traditional Medicinal Plant, Planchonia careya (Lecythidaceae)

Author

Jacqui McRae, Qi Yang, Russell Crawford and Enzo Palombo

Proceeding

Traditional & Complementary Medicine Exhibition 2007 (TCME 2007),Putra World Trade Centre (PWTC), Kuala Lumpur, Malaysia

Date

17/7/2007

Keyword

Planchonia careya, Staphylococcus aureus, antibacterial

Abstract

The pulped leaves of the common tropical Australian tree,Planchonia careya, have been traditionally used as a wound healing agent. For this reason, they were investigated for antibacterial activity and the compounds producing this observed activity were isolated and characterised. Activity-guided fractionation was used to separate the antibacterial compounds from the crude aqueous and methanolic leaf extracts, utilizing many different types of media including XAD-16 resin, LH20 gel, C18 media, and silica gel. Isolated compounds were characterised by 1D and 2D NMR spectroscopy (1H,13C, COSY HSQC, HMBC) and mass spectroscopy (MS), as well as comparisons with the literature. Antibacterial activity was assessed using plate-hole diffusion assays with 10¿L of sample in each 4mm well. Proanthocyanidins proved to be responsible for the observed antibacterial activity against Gram positive bacteria in the aqueous extract. The isolated compounds were identified as the flavan-3-ol, (+)-gallocatechin, and the prodelphinidin, gallocatechin-(4α-8)-gallocatechin. Both compounds showed promising activity against methicillin-resistantStaphylococcus aureus(MRSA), while exhibiting no toxic effect against MA104 (rhesus monkey kidney) cells in the preliminary cytotoxicity assays. This suggests that these proanthocyanidins may have potential as antibiotics. A known pentacyclic triterpenoid, hyptatic acid-A, as well as the fatty acids 9-hydroxy-10E, 12Z-octadecadienoic acid (9-HODE) and 9-hydroxy-10E,12Z,15Z-octadecatrienoic acid (9-HOTrE) contributed to the activity of the methanolic extract against Gram positive and Gram negative bacteria. The assignment of the aliphatic chain carbons for 9-HODE was achieved by comparison with the similar shifts of the 9-HOTrE spectra, and the structure of hyptatic acid-A was confirmed by comparison of the1H shifts and optical rotation with that of the literature. The elucidation of five known antibacterial compounds from the leaf extracts ofP. careyavalidates the use of this species in wound-healing, and with further investigation these compounds may prove beneficial in the fight against infectious diseases.