Identification of (2E,4Z,7Z)-Decatrienoic Acid in Noni Fruit and Its Use in Quality Screening of Commercial Noni Products

Abstract

The fruit of noni (Morinda citrifolia L.) has been used traditionally as food and for medicinal purposes for over 2,000 years. Today, hundreds of different brands of noni fruit juices appear on the market. In this study, we provide an analytical method for the quality assurance of noni fruit juices based on the determination of two organic (scopoletin and (2E,4Z,7Z)-decatrienoic acid (DTA)) and one inorganic marker substances (potassium). DTA was observed in noni fruit for the first time. A total of 32 authentic and 16 commercially produced noni fruit juices were investigated. In non-processed authentic noni fruit juices, DTA was almost completely present as a glycoside, whereas considerable amounts of free DTA occurred in commercial juices. Concentration of noni juice by heat evaporation reduces the amount of DTA compared to other non-volatile marker compounds, such as scopoletin. It is therefore possible to distinguish between noni juices prepared with or without fermentation or by rehydration of noni fruit juice concentrates. The degree of dilution of commercial noni fruit juices was also easily detectable by determination of the potassium content, which should be in the range of 1,000–3,000 mg/L, as determined in authentic noni fruit juices.