Aim: Confirm the use of Plectanthus spp. plants in traditional medicine, particularly as anti-inflammatory and anti-infective agents.
Materials & methods: Compounds previously isolated from Plectranthus spp. were studied for their anti-inflammatory activity using the SNAP assay and RAW 264.7 cells, by the quantification of nitric oxide. An halimane diterpene and its derivatives were tested in infected macrophages with M. tuberculosis H37Rv, using CFU counts assay, at their minimum inhibitory concentration values. Results: The isolated compounds tested at noncytotoxic concentrations, did not reveal nitric oxide scavenging in the S-nitroso-N-acetylpenicillamine and the cellular assays. On the other hand, promising results were obtained regarding one semisynthetic halimane derivative (11R*,13E)-halima-5,13-diene-11,15-diol), previously prepared (2.1 × 105 CFU/mL), with an effect similar to the antitubercular drugs ethambutol (2.0 × 105 CFU/mL) and isoniazid (1.2 × 105 CFU/mL).
Conclusion: The present report demonstrates the relevance of Plectranthus spp. in medicinal chemistry drug development for TB and other infective respiratory complaints. Also, this work suggests that further studies involving other inflammatory mediators are needed to validate the anti-inflammatory use of these medicinal plants.
Keywords: Mycobacterium tuberculosis; Plectranthus spp.; SNAP; anti-inflammatory; terpenoids; tuberculosis.