Immune-enhancing screening of thirteen plant extracts from Indonesia and synergistic effect of combination extract on murine macrophage-like RAW 264.7 cells

Indonesian people use traditional herbal medicines to protect the body from infectious agents. This study examines the potential immune-enhancing activity of selected Indonesian plants and extract combinations on RAW 264.7 cells. Thirteen extracts from seven plants were macerated with ethanol and water for 24 h. A viability assay was conducted to identify the safe concentration of extract using MTT method. The immune-enhancing activity of extracts was evaluated using Griess method to quantify nitric oxide (NO) generation in RAW 264.7 cells. Among thirteen extracts, 70% ethanolic extract of Centella asiatica leaf (CA70), 50% ethanolic extract of Anredera cordifolia (Ten.) leaf (AC50), 50% ethanolic extract of Curcuma xanthorrhiza rhizome (CX50) and water extract of Morinda citrifolia fruit (MCW) at 10 µg/ml stimulated NO generation on RAW 264.7 cells relative to an untreated group. Six combination extracts were tested, and the result showed that a combination of CX50 and MCW exhibited the highest NO levels compared to other formulas. It significantly increased NO production on RAW 264.7 cells starting at 0.625 µg/ml and exhibited a higher NO level than each extract. It can be concluded that both extracts exhibited immune-enhancing activity on RAW 2647 cells, and the formula extracts demonstrated synergistic immunostimulatory activity.