Traditional preparation of Phaleria nisidai, a Palauan tea, reduces exposure to toxic daphnane-type diterpene esters while maintaining immunomodulatory activity

Abstract

The presence of daphnane diterpene esters in a frequently consumed traditional beverage was initially viewed as a public health concern, though interview data reveal that Palauans do not observe toxicity or side effects associated with their use of P. nisidai tea. Concurrently, daphnanes are present in methanolic extracts but not detected in aqueous preparations indicating that the traditional method of preparation avoids the extraction of these potentially toxic compounds, while still maintaining immunostimulant activity.

Genkwanin glycosides from the Phaleria nisidai extract improve glucose homeostasis by stimulating insulin-independent glucose uptake.

“…(Thymelaeaceae) were collected at the time of the clinical study (Kitalong et al, 2017) and reference specimens were deposited at the Belau National Museum Herbarium. The leaves of PN were extracted by decoction according to the traditional recipe used by the population of Palau (Kulakowski et al, 2015). The dried leaves were extracted by decoction for 1 hour, then freeze-dried to facilitate mouse feeding and chemical investigation.…”

“…The dried leaves were extracted by decoction for 1 hour, then freeze-dried to facilitate mouse feeding and chemical investigation. The decoction was performed without a lid to evaporate potentially irritating compounds since the leaves have been reported to contain toxic volatile compounds removed upon boiling (Kulakowski et al, 2015). After filtration (60°C ± 5°C) and first evaporation with rotavapor to reduce the water quantity (Büchi SARL, Rungis, France), the decoction was freeze-dried (-80°C, 0.01 bar, Christ Alpha 2-4 LD plus, Osterode am Harz, Germany) and stored at 4°C.…”