title: Antioxidant and anti-inflammatory activity of Ocimum labiatum extract and isolated labdane diterpenoid.
abstract: 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.
authors.affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria, 0002 South Africa ; Present address: Chemistry & Biochemistry department, Faculty of Science, University of Namibia, Windhoek, 9000 Namibia.
authors.forename: Petrina
authors.initials: P
authors.lastname: Kapewangolo
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Box 2050, Johannesburg, South Africa ; Present address: Department of Traditional Medicine, National Institute for Medical Research, P. O Box 9653, Dar es Salaam, Tanzania.
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Omolo
authors.affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria, 0002 South Africa.
authors.forename: Ronel
authors.initials: R
authors.lastname: Bruwer
authors.affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria, 0002 South Africa.
authors.forename: Pascaline
authors.initials: P
authors.lastname: Fonteh
authors.affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria, 0002 South Africa ; Present address: Department of Biochemistry, Faculty of Sciences, University of Johannesburg, P.O. Box 524, Auckland Park, Johannesburg, 2006 South Africa.
authors.forename: Debra
authors.initials: D
authors.lastname: Meyer
keywords: AP-1; Antioxidant; Inflammatory cytokines; Labdane diterpenoid; Nitric oxide; Ocimum labiatum