Immunostimulatory effects of the traditional palauan adaptogen Phaleria nisidai Kaneh

Phaleria nisidai Kaneh., locally known as delalakar or "the Mother of medicines," is a tree in the Thymeleaeaceae family with modern and historical use in the Micronesian country of Palau as an invigorating, strengthening, and healing prophylactic beverage. In an attempt to evaluate its traditional use as an adaptogen, extracts of P. nisidai were tested on human peripheral blood mononuclear cells (PBMC) to determine if there are immunostimulatory effects. Methanol (PNM) and water (PNW) extracts of P. nisidai were prepared by refluxing for two hours. PBMCs were isolated from healthy donor blood and cultured in 10% HS/RPMI media supplemented with low concentrations of PNM and PNW for up to 72 hours. Cytotoxicity and cell proliferation were measured by using the MTT assay on cells in culture. Cell-free supernatant was used to determine secretion of IFNγ by PBMCs in the ELISA assay. Both organic and traditional water extracts of P. nisidai were able to stimulate proliferation and IFNγ-secretion of PBMCs dose- and time-dependently. The superantigen Staphyloccus enterotoxin B (SEB) showed IFNγ-releasing activity but did not cause an increase in PBMC proliferation. Phaleria nisidai was able to stimulate both cell proliferation and IFNγ, unlike the nonspecific T-cell activating SEB, which was only able to induce cytokine release. These results demonstrate that P. nisidai may have cellular immunity-enhancing effects, supporting its traditional use as a healing adaptogenic beverage.