Influence of Plant Origins and Seasonal Variations on Nutritive Values, Phenolics and Antioxidant Activities of Adenia viridiflora Craib., an Endangered Species from Thailand

Adenia viridiflora Craib. is an indigenous plant found in Thailand, Cambodia and Vietnam that has become threatened owing to lack of knowledge about its agricultural management. This plant is now rare in the wild and was registered in the Plant Genetic Conservation Project under the initiation of Her Royal Highness Princess Maha Chakri Sirindhorn (RSPG) to promote sustainable conservation and optimally beneficial utilization. A. viridiflora has a long history of utilization as a nutrient-rich source with medicinal properties but scientific evidence of the veracity of these claims is limited. Here, the nutritional compositions, phenolic contents and antioxidant activities of different plant parts (young shoots and old leaves) of A. viridiflora were investigated using plants collected from four areas of Thailand as Kamphaeng Phet (KP), Muang Nakhon Ratchasima (MN), Pakchong Nakhon Ratchasima (PN) and Uthai Thani (UT) at different harvesting periods (March-April, May–June and July–August). Results indicated that young shoots provided higher energy, protein, fat, dietary fiber, phosphorus, sodium, and zinc than old leaves. By contrast, nutrients such as total sugar, vitamin C, carotenoids, potassium, calcium, magnesium, and iron contents were higher in old leaves that also exhibited higher phenolic contents and most antioxidant activities than young shoots. Generally, most nutrients, phenolic contents, and antioxidant activities exhibited no clear trend among different plant origins. The harvesting period of July–August provided a suitable climate for biosynthesis of most nutrients, while high phenolics were mainly found in samples harvested in March–April. No clear trend was observed in the prevalence of antioxidant activities that varied according to assay techniques.