LC-MS/MS-based metabolomics approach identified novel antioxidant flavonoids associated with drought tolerance in citrus species

Abstract

Citrus fruits are cultivated around the world, and they face drought stress frequently during their growth and development. Previous studies showed that citrus plants biosynthesized flavonoid compounds in response to abiotic stress. In this study, we have quantified 37 flavonoid compounds from the leaves of three distinct citrus species including sour orange (drought-tolerant), pummelo ‘Majia you pummelo’ (drought-sensitive), and lemon (drought-sensitive). The 37 flavonoids consisted of 12 flavones, 10 flavonols, 6 flavanones, 5 isoflavanones, and 1 each for chalcone, flavanol, flavanonol, and flavone glycoside. Drought stress differentially altered the flavonoid metabolism in drought-tolerant and drought-sensitive citrus species. The kaempferol 3-neohesperidoside was 17-fold higher in sour orange (124.41 nmol/L) after 18 days of drought stress than lemon (7.33 nmol/L). In sour orange, neohesperidin (69.49 nmol/L) was 1,407- and 37-fold higher than pummelo and lemon, respectively. In sour orange, some flavonoids were significantly increased, such as vitexin, neohesperidin, cynaroside, hyperoside, genistin, kaempferol 3-neohesperidoside, eriocitrin, and luteolin, in response to drought stress, whereas in lemon, these flavonoids were significantly decreased or not altered significantly in response to drought stress. Moreover, the total contents of flavonoids and antioxidant activity were increased in sour orange as compared with pummelo and lemon. The genes associated with flavonoid biosynthesis (PAL, CHI, FLS, GT1, F3H, F3’M, C4H, 4CL, FLS, FG2, FG3, and CYP81E1) were more highly expressed in sour orange leaves than in pummelo and lemon after drought stress. These outcomes showed that pummelo and lemon failed to biosynthesize antioxidant flavonoids to cope with the prolonged drought stress, whereas the sour orange biosynthesized fortified flavonoid compounds with increased antioxidant activity to detoxify the harmful effects of reactive oxygen species produced during drought stress.

Metabolomic and Transcriptomic Analyses Provide New Insights into Health-Promoting Metabolites from Cannabis Seeds Growing in the Bama Region of China

“…Vitexin shows various biological activities, including antioxidant, anticancer, and anti-inflammatory activities [32,33]. Choline is an essential nutrient for liver, muscle, and brain function, and both choline and choline alfoscerate have been shown to have anti-Alzheimer activity [9,34]. These findings suggest that hemp seeds from the Bama region provide various health benefits, and this might contribute to the good physical health of the local people.…”

“…Previous studies have shown that hemp seeds are rich in flavonoid metabolites [5,8]. Flavonoids also exhibit diverse biological activities, including anticancer, antidiabetic, antiviral, anti-heart disease, antimicrobial, antioxidant, and anti-Alzheimer activities, and have been shown to promote the homeostasis of the intestinal flora [9][10][11][12][13][14][15]. The oil of hemp seeds also provides various health benefits; previous studies have shown that it contains more polyunsaturated fatty acids and rare fatty acids, such as γ-linolenic acid and stearidonic acid, compared with other cooking oils [16,17].…”

Effects of the Cultivation Methods on the Sensory Quality and Phytochemical Profiles of Satsuma Mandarin (Citrus unshiu)

“…Previous studies showed that the soil water content and sunlight exposure affected the secondary metabolite profile and volatile compound levels of white grapes [38], quince [18], and grape berry [39]. A low soil water content causes drought and salt stress in citrus plants, resulting in reduced plant growth and leaf area, which ultimately affects photosynthesis, respiration, and metabolite profiles [40][41][42]. Moderate drought stress decreases the content of citric and malic acids in fruits such as nectarines [43] and grapes [44], which is in line with our results (Figure 3), whereas the opposite was reported for ponkan fruits grown in soil with 40% maximum water capacity under water stress [45].…”

Phenylpropanoid Metabolism in Phaseolus vulgaris during Growth under Severe Drought

“…Similarly, flavonoid and phenolic acid concentrations were little affected in the leaves of Amaranthus cruentus L. when water was withheld from greenhouse-cultivated plants for 6 days [ 31 ]. Moreover, Rao et al [ 32 ] determined that a greater proportion of leaf flavonoid constituents were elevated in a drought-tolerant sour orange and to a higher magnitude after 18 days of drought, whereas fewer metabolites were impacted in the leaves of a drought-sensitive lemon. Thus, there appears to be a discrepancy as to whether phenylpropanoids accumulate with drought.…”