Kava is the traditional intoxicating beverage of the Pacific with mild sedative and muscle relaxant effects, which are attributed to a group of compounds known as kavalactones. This paper aims to evaluate the quality of kava sold in the local markets of Fiji through the quantification of the six major kavalactones in kava root bundles and powdered kava packages using ethanolic extracts and HPLC. It was found in this work that kava root bundles contain mainly noble kava roots with a total kavalactone content of 8–13%; kavain had the highest concentration among kavalactones and kavain, methysticin, and yangonin together represented 69–71% of the total kavalactone content. Adulteration via mixing noble kava roots with those of non-noble kava with a relatively high dihydrokavain and dihydromethysticin content has also been observed. Powdered kava products were found to contain lower amounts of kavalactones (3–5%) with a less favorable kavalactone profile than those of root bundles, possibly due to mixing roots, rhizomes, and/or basal stems. The findings of this work, namely the variation in kavalactone content and profile in marketed products, indicate the need for rigorous quality control and quality indicators on kava commodities. Suggestions to include quantitative measures in the previously proposed chemical standardization code are also presented.

The kava beverage of the Pacific is known for its intoxicating, soothing and relaxing effects, attributed to a group of compounds (called kavalactones) produced by the kava plant. An unfavorable kavalactone profile, however, contributes to side effects, including hepatotoxicity. Therefore, the chemical quality of kava is of key importance for consumer safety. This work investigated the chemical quality of the kava cultivated on the Taveuni, Qamea, and Rabi Islands by quantifying the main kavalactones in the roots and rhizomes of eighty-eight kava plants using the HPLC method. It was concluded that the farmers in these regions almost exclusively grow classified noble kava cultivars with a favorable kavalactone profile; the total kavalactone concentration varies between 7.2–14.1 wt.% and 4.7–8.2 wt.% in the dried roots and rhizomes, respectively. Kavain is the major kavalactone component (27–34 wt.% of the total amount of kavalactones), followed by methysticin, yangonin, or dihydrokavain in the roots, and dihydrokavain or methysticin in the rhizomes, respectively. One unclassified non-noble cultivar, with elevated levels of non-desirable dihydrokavain, dihydromethysticin, and flavokavains, is also identified and characterized.

Piper methysticum G. Forst. (kava) is an important horticultural shrub of the Pacific, used as an ingredient of the intoxicating kava beverage, dietary supplement, and medicine around the globe. This study presents the first systematic evaluation of the phytochemical composition and nutrition values of roots and rhizomes of kava cultivated on three key kava-growing areas of Fiji (Rotuma, Kadavu, and Vanua Levu) by quantifying their kavalactone and flavokavain content, as well as measuring their calorific value, protein concentration and ash contents. Dried roots and rhizomes of the studied cultivars exhibited relatively high kavalactone concentrations (8.9–13.8 and 3.9–8.9 wt.%, respectively); favorable lactone profiles, with kavain as the major lactone component (2.1–4.6 and 1.1–2.6 wt.%, respectively); and low flavokavain contents (below 0.25 wt.%). The protein and ash contents of roots were measured to be 2.7–5.0 wt.% and 3.2–6.2 wt.%, respectively, and calorific values of roots were measured as 17.1–19.4 MJ·kg⁻¹—values that are systematically higher than those found for rhizomes (1.6–3.2 wt.%, 2.3–4.6 wt.%, and 16.5–17.7 MJ·kg⁻¹, respectively). A positive relationship between the calorific value and total kavalactone content was observed. A novel, unclassified kava cultivar (named Matanitabua) was discovered in Vanua Levu and identified as a noble kava cultivar.