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Ethnopharmacological Relevance: Preparations from Munronia pinnata (Wall.) Theob. are extensively used in traditional medicine in Sri Lanka for the treatment of inflammatory conditions. However, neither the pharmacological features nor the phytochemistry of this plant are explored in order to understand and rationalize the reported ethnobotanical significance. As 5-lipoxygenase (5-LO) and microsomal prostaglandin E2 synthase (mPGES)-1 are crucial enzymes in inflammatory disorders, we evaluated their inhibition by M. pinnata extracts and studied the chemical profile of the plant for the identification of relevant constituents., Materials and Methods: Cell-free and cell-based assays were employed in order to investigate the suppression of 5-LO and mPGES-1 activity. Cell viability, radical scavenger activities, and inhibition of reactive oxygen species formation (ROS) in neutrophils were studied to assess cytotoxic and antioxidant effects. Gas and liquid chromatography coupled to mass spectrometric analysis enabled the characterization of secondary metabolites., Results: The n-hexane extract of M. pinnata efficiently suppressed 5-LO activity in stimulated human neutrophils (IC50 =8.7µg/ml) and potently inhibited isolated human recombinant 5-LO (IC50 =0.48µg/ml) and mPGES-1 (IC50 =1.0µg/ml). In contrast, no significant radical scavenging activity or suppression of ROS formation was observed, and neutrophil viability was unaffected. The phytochemistry of the plant was unveiled for the first time and phytosterols, fatty acids, sesquiterpenes and several other types of secondary metabolites were identified., Conclusions: Together, potent inhibition of 5-LO and mPGES-1 activity, without concomitant antioxidant activity and cytotoxic effects, rationalizes the ethnopharmacological use of M. pinnata as anti-inflammatory remedy. Detailed chromatographic/mass spectrometric analysis reveals discrete chemical structures of relevant constituents., (© 2013 Published by Elsevier Ireland Ltd.)

Ethnopharmacological Relevance: The perennial herb Plectranthus zeylanicus Benth is extensively used in traditional medicine in Sri Lanka and South India for treating inflammatory conditions, but pharmacological features of Plectranthus zeylanicus are hardly explored in order to understand and rationalize its use in ethnomedicine. As 5-lipoxygenase (5-LO) is a key enzyme in inflammatory disorders such as asthma or atherosclerosis, we investigated 5-LO inhibition by Plectranthus zeylanicus extracts and analyzed relevant constituents., Materials and Methods: We applied cell-free and cell-based assays to investigate suppression of 5-LO activity. Cell viability, radical scavenger activities, and inhibition of reactive oxygen species formation (ROS) in neutrophils were analysed to exclude unspecific cytotoxic or antioxidant effects. Constituents of the extracts were characterized by bioassay-guided fractionation and by analysis using gas or liquid chromatography coupled to mass spectrometric (Orbitrap) analysis., Results: Extracts of Plectranthus zeylanicus prepared with n-hexane or dichloromethane potently suppressed 5-LO activity in stimulated human neutrophils (IC50=6.6 and 12µg/ml, respectively) and inhibited isolated human recombinant 5-LO (IC50=0.7 and 1.2µg/ml, respectively). In contrast, no significant radical scavenging activity or suppression of ROS formation was observed, and neutrophil viability was unaffected. Besides ubiquitously occurring ingredients, coleone P, cinncassiol A and C, and callistric acid were identified as constituents in the most active fraction., Conclusions: Together, potent inhibition of 5-LO activity, without concomitant anti-oxidant activity and cytotoxic effects, rationalizes the ethnopharmacological use of Plectranthus zeylanicus as anti-inflammatory remedy. Modern chromatographic/mass spectrometric analysis reveals discrete chemical structures of relevant constituents., (© 2013 Elsevier Ireland Ltd. All rights reserved.)