Analytical and pharmacological investigation of Ocotea bullata (black stinkwood) bark and leaves

Ocotea bullata (Lauraceae), one of the top-ten traditional medicinal plants used in KwaZulu-Natal, is close to extinction through high demand and dest ructive harvesting methods. The stem bark is traditionally used to cure hea daches, urinary disorders and stomach problems. Substitution of leaves for bark provides a possible resource management solution for this threatened m edicinal plant. One aim of this study was to compare the chemical compositi on of O. bullata leaves and bark using TLC, HPLC and GC-MS analysis. The ch aracteristic analytical fingerprints of leaf and bark extracts showed great similarities. A second aim was to investigate the pharmacological properti es of O. bullata as a remedy against headaches. Leaf and bark extracts were tested in terms of cyclooxygenase-1 and 5-lipoxygenase inhibition. Extract s from the bark exhibited moderate inhibitory activity in both test systems . Extracts from fresh leaves were superior to bark extracts in terms of the ir in vitro inhibitory activity against cyclooxygenase-1 and 5-lipoxygenase . Volatiles obtained from n-hexane extracts of leaves and bark showed bette r inhibitory activity towards cyclooxygenase-1 and especially towards 5-lip oxygenase than the original n-hexane extracts. Volatiles were therefore rec ognized as one of the main active principles in O. bullata with regards to the anti-inflammatory properties of this medicinal plant. This lends suppor t to the traditional usage of O. bullata bark as an inhalant or snuff. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.