Phytochemical Diversity and Antioxidant Potential of Natural Populations of Nelumbo nucifera Gaertn. throughout the Floristic Regions in Thailand

Abstract

Asian lotus has long been consumed as a food and herbal drug that provides several health benefits. The number of studies on its biological activity is significant, but research at the population level to investigate the variation in phytochemicals and biological activity of each population which is useful for a more efficient phytopharmaceutical application strategy remains needed. This present study provided the frontier results to fill-in this necessary gap to investigating the phytopharmaceutical potential of perianth and stamen, which represent an important part for Asian traditional medicines, from 18 natural populations throughout Thailand by (1) determining their phytochemical profiles, such as total contents of phenolic, flavonoid, and anthocyanin, and (2) determining the antioxidant activity of these natural populations using various antioxidant assays to examine different mechanisms. The result showed that Central is the most abundant floristic region. The stamen was higher in total phenolic and flavonoid contents, whereas perianth was higher in monomeric anthocyanin content. This study provided the first description of the significant correlation between phytochemical contents in perianth compared with stamen extracts, and indicated that flavonoids are the main phytochemical class. This analysis indicated that the stamen is a richer source of flavonoids than perianth, and provided the first report to quantify different flavonoids accumulated in stamen and perianth extracts under their native glycosidic forms at the population level. Various antioxidant assays revealed that major flavonoids from N. nucifera prefer the hydrogen atom transfer mechanism when quenching free radicals. The significant correlations between various phytochemical classes and the different antioxidant tests were noted by Pearson correlation coefficients and emphasized that the antioxidant capability of an extract is generally the result of complex phytochemical combinations as opposed to a single molecule. These current findings offer the alternative starting materials to assess the phytochemical diversity and antioxidant potential of N. nucifera for phytopharmaceutical sectors.

Keywords: Nelumbo nucifera; Nelumbonaceae; antioxidant potential; floristic regions; phytochemical profiles; population level; sacred lotus.

Figure 1

The distribution map of N. nucifera 18 populations collected from the natural habitat cover the floristic region in Thailand. The number 1–18 in the map indicates the population number.

Figure 2

N. nucifera: (A,B). Natural habitats; (C–T). Perianth of Population No. 1–18, respectively; (U). Stamen of Population No. 1–18, respectively; Bar scale = 1 cm. Photo are taken in Thailand by Duangjai Tungmunnithum.

Figure 3

Ternary plot showing the visualization of the relative proportion of TPC, TFC, and TAC within the stamen (A) and perianth (B) extracts of 18 N. nucifera populations originating from various floristic regions from Thailand.

Figure 4

HPLC chromatograms (recorded at 320 nm) of the the stamen (A) and perianth (B) extracts of 18 N. nucifera populations originating from various floristic regions from Thailand. Quantification of the main flavonoids in the stamen (C) and perianth (D) extracts of 18 N. nucifera populations originating from various floristic regions from Thailand. Myr-3-O-Glc: myricetin-3-O-glucose; Quer-3-O-GlcA: quercetin-3-O-glucuronic acid; Kae-3-O-Rob: kaempferol-3-O-robinobiose; Kae-3-O-Glc: kaempferol-3-O-glucose; Kae 3-O-GlcA: kaempferol 3-O-glucuronic acid; Iso-3-O-Glc: isorhamnetin-3-O-glucose; the mean and standard deviation of the concentration of each flavonoid is provided in Table S1.

Figure 5

Hierarchical clustering analysis dendrogram according to the phytochemical composition of the stamen and perianth extracts of 18 N. nucifera populations originating from various floristic regions from Thailand. The percentages of replicate trees in which associated samples cluster together in the bootstrap test (percentage of 5000 replicates) are indicated next to the branches.

Figure 6

Ternary plot showing the visualization of the relative contribution of the different in vitro assays (ABTS, DPPH and FRAP) to the antioxidant capacitiy of the stamen (A) and perianth (B) extracts of 18 N. nucifera populations originating from various floristic regions from Thailand.

Figure 7

Principal component analysis (PCA) linking the phytochemical profile and antioxidant capacity of the stamen and perianth extracts of 18 N. nucifera populations originating from various floristic regions from Thailand. Variance of component 1 = 97.42% and component = 2.33%. S: stamen extract; P: perianth extract; each number in blue represents the different populations. The corresponding loading score plots for components 1 and 2 are presented in Figure S1.