Traditionally Used Thai Medicinal Plants: in Vitro Anti-inflammatory, Anticancer and Antioxidant Activities

Aims Of The Study: In order to assess traditional Thai claims about the therapeutic potential of medicinal plants and to select plants for future phytochemical research, nine plant species with anti-inflammatory uses were selected from Thai textbooks and assessed for their in vitro anti-inflammatory, antiproliferative and antioxidant activities.

Methods: Nuclear factor-kappaB (NF-kappaB) inhibitory effects in stably transfected HeLa cells were determined by luciferase assay, and effects on LPS-induced pro-inflammatory mediators prostaglandin E2 (PGE2), interleukin (IL)-6, IL-1beta, and tumour necrosis factor (TNF)alpha in primary monocytes were assessed by ELISA. Cytotoxic activities were examined against HeLa cells, human leukaemia CCRF-CEM cells and the multidrug-resistant CEM/ADR5000 subline using the MTT and XTT tests. However, a redox status has been linked with both inflammation and cancer, antioxidant effects were also assessed using the DPPH, lipid-peroxidation, and Folin-Ciocalteau methods.

Results: Among all the nine species, Gynura pseudochina var. hispida and Oroxylum indicum showed the most promising NF-kappaB inhibitory effects with the lowest IC(50) values (41.96 and 47.45 microg/ml, respectively). Muehlenbeckia platyclada did not inhibit the NF-kappaB activation but effectively inhibited the release of IL-6, IL-1beta and TNF-alpha with IC(50) values ranging between 0.28 and 8.67 microg/ml. Pouzolzia indica was the most cytotoxic against CCRF-CEM cells and the multidrug-resistant CEM/ADR5000 cells (9.75% and 10.48% viability, at 10 microg/ml, respectively). Rhinacanthus nasutus was the most potent cytotoxicity against HeLa cells (IC(50) 3.63 microg/ml) and showed specific cytotoxicity against the multidrug-resistant CEM/ADR5000 cells (18.72% viability at 10 microg/ml, p<0.0001 when compared to its cytotoxicity against CCRF-CEM cells). Moreover, Oroxylum indicum showed a high level of antioxidant activity by inhibiting lipid-peroxidation (IC(50) 0.08 microg/ml).

Conclusions: This study provides in vitro evidence for the use of the Thai plants, most importantly Gynura pseudochina var. hispida, Oroxylum indicum and Muehlenbeckia platyclada as Thai anti-inflammatory remedies and these plants are now a priority for further phytochemical research.