Antioxidant and anti-inflammatory activity of Ocimum labiatum extract and isolated labdane diterpenoid

Background: plants from the genus ocimum are used as folk medicine for treating various diseases including inflammatory and immune-related diseases. numerous reports have suggested plant extracts and their constituents as possible anti-inflammatory agents. here,in vitro evidence of ocimum labiatum's immune-enhancing and antioxidant properties is presented for the first time. methods: the anti-inflammatory effect of o. labiatum ethanolic extract and an isolated diterpenoid was determined using a cytometric bead array (cba) technique. the effect on phytohemagglutinin (pha)-induced nitric oxide (no) production in peripheral blood mononuclear cells (pbmcs) was also assessed. a battery of antioxidant assays were used for detecting antioxidant activity while the anti-inflammatory mechanism was evaluated using an elisa-based activator protein (ap-1) (c-jun) assay. cytotoxicity was determined on tzm-bl and pbmcs using a tetrazolium dye and confirmed by a novel label-free real-time assay. results: a 25 μg/ml non-cytotoxic concentration of o. labiatum extract significantly (p < 0.05) inhibited the production of pro-inflammatory cytokines; il-2,il-4,il-6 and il-17a. except for the dual acting pro- or anti-inflammatory cytokine,il-6,which was upregulated,a non-cytotoxic 50 μm concentration of the isolated labdane diterpenoid compound significantly (p < 0.05) decreased the production of all the pro-inflammatory cytokines. in the anti-inflammatory pathway studies,the compound also inhibited ap-1 significantly (p < 0.05) at 50 μm. the extract demonstrated strong,dose dependent antioxidant activity with ic50 values ranging from 13 ± 0.8 to 54.86 ± 1.28 μg/ml while the terpene had no antioxidant property. the extract and diterpenoid decreased the production of the inflammatory mediator no,at non-cytotoxic concentrations. the cc50 of the extract in tzm-bl and pbmcs was 62.6 ± 0.6 and 30.1 ± 0.4 μg/ml while that of the compound was 112.6 ± 0.2 and 70 ± 0.4 μm respectively. the real time studies confirmed tetrazolium dye assessed viability and also detected a unique growth pattern for the plant materials compared to untreated cells. conclusions: o. labiatum extract demonstrated promising anti-inflammatory and antioxidant properties while the terpenoid showed anti-inflammatory but no antioxidant activity. the anti-inflammatory mechanism of the terpene was a result of inhibition of ap-1. these data represents promising first steps towards the development of naturally derived anti-inflammation drugs. © 2015 kapewangolo et al.