Relationship between the Composition of Flavonoids and Flower Colors Variation in Tropical Water Lily (Nymphaea) Cultivars

Water lily, the member of the Nymphaeaceae family, is the symbol of Buddhism and Brahmanism in India. Despite its limited researches on flower color variations and formation mechanism, water lily has background of blue flowers and displays an exceptionally wide diversity of flower colors from purple, red, blue to yellow, in nature. In this study, 34 flavonoids were identified among 35 tropical cultivars by high-performance liquid chromatography (HPLC) with photodiode array detection (DAD) and electrospray ionization mass spectrometry (ESI-MS). Among them, four anthocyanins: delphinidin 3-O-rhamnosyl-5-O-galactoside (Dp3Rh5Ga), delphinidin 3-O-(2″-O-galloyl-6″-O-oxalyl-rhamnoside) (Dp3galloyl-oxalylRh), delphinidin 3-O-(6″-O-acetyl-β-glucopyranoside) (Dp3acetylG) and cyanidin 3- O-(2″-O-galloyl-galactopyranoside)-5-O-rhamnoside (Cy3galloylGa5Rh), one chalcone: chalcononaringenin 2′-O-galactoside (Chal2′Ga) and twelve flavonols: myricetin 7-O-rhamnosyl-(1→2)-rhamnoside (My7RhRh), quercetin 7-O-galactosyl-(1→2)-rhamnoside (Qu7GaRh), quercetin 7-O-galactoside (Qu7Ga), kaempferol 7-O-galactosyl-(1→2)-rhamnoside (Km7GaRh), myricetin 3-O-galactoside (My3Ga), kaempferol 7-O-galloylgalactosyl-(1→2)-rhamnoside (Km7galloylGaRh), myricetin 3-O-galloylrhamnoside (My3galloylRh), kaempferol 3-O-galactoside (Km3Ga), isorhamnetin 7-O-galactoside (Is7Ga), isorhamnetin 7-O-xyloside (Is7Xy), kaempferol 3-O-(3″-acetylrhamnoside) (Km3-3″acetylRh) and quercetin 3-O-acetylgalactoside (Qu3acetylGa) were identified in the petals of tropic water lily for the first time. Meanwhile a multivariate analysis was used to explore the relationship between pigments and flower color. By comparing, the cultivars which were detected delphinidin 3-galactoside (Dp3Ga) presented amaranth, and detected delphinidin 3′-galactoside (Dp3′Ga) presented blue. However, the derivatives of delphinidin and cyanidin were more complicated in red group. No anthocyanins were detected within white and yellow group. At the same time a possible flavonoid biosynthesis pathway of tropical water lily was presumed putatively. These studies will help to elucidate the evolution mechanism on the formation of flower colors and provide theoretical basis for outcross breeding and developing health care products from this plant

Putative flavonoid biosynthesis pathway related to flower color of tropical water lily.

<p>The red arrows indicate the biosynthesis pathway of anthocyanins, the dotted arrows indicate uncertain reaction. Cy: cyanidin; Dp: delphinidin; Qu: quercetin; Km: kaempferol; My: myricetin; Is: isorhamnetin; Ga: glactoside; G: glucoside; Rh: rhamnoside; CHS: chalcone synthase; CHI : chalcone isomerase, F3H: flavonoid 3-hydroxylase; F3′H: flavonoid 3′-hydroxylase; F3′5′H: flavonoid 3′,5′-hydroxylase; DFR: dihydroflavonol reductase; FLS: flavonol synthase; ANS: anthocyanidin synthase; GT: flavonoid glycosyltransferase; AT: acyltransferase; MT: methyltransferase; CoA: acetyl coenzyme A.</p

Flower color distribution of Tropical water lily cultivars in coordinate systems of bivariate (<i>a</i>^* and <i>b</i>^*) (A) and trivariate (<i>a</i>^*, <i>b</i>^*, and <i>L</i>^*) (B), respectively.

<p>The flower colors were identified by the RHSCC value.</p

The HPLC profiles of glycosides of flavonol and chalcone in water lily petals (detected at 350 nm).

<p>The HPLC profiles of glycosides of flavonol and chalcone in water lily petals (detected at 350 nm).</p

Petal colors and color parameters of 35 cultivars of water lily.

1<p>The name of water lily cultivar;</p>2<p>RHSCC: Royal Horticultural Society Colour Chart;</p>3<p><i>L</i>^*, lightness; <i>a</i>^*, <i>b</i>^*, chromatic components; <i>C</i>^*, chroma, <i>C</i>^* = (<i>a</i>^*2+<i>b</i>^*2)^1/2; <i>h</i>, hue angle (u), <i>h</i> = arctan (<i>b</i>^*/<i>a</i>^*);</p>4<p>TA: total anthocyanins; TF: total flavonols and chalcones in mg per 1 g fresh petals;</p>5<p>CI: copigment index = TF/TA; “∞”: means samples without glycosides of anthocyanin.</p

Nine representative flower colors, ‘Ai Ji Bai’ (A), 18 (B), 27 (C), ‘Albert Greenberg’ (D), 34 (E), ‘Eldorado’ (F), 37 (G), ‘Roxburgh’ (H), and ‘Tai Guo Wang’ (I), for water lily cultivars sampled from a natural population.

<p>Nine representative flower colors, ‘Ai Ji Bai’ (A), 18 (B), 27 (C), ‘Albert Greenberg’ (D), 34 (E), ‘Eldorado’ (F), 37 (G), ‘Roxburgh’ (H), and ‘Tai Guo Wang’ (I), for water lily cultivars sampled from a natural population.</p

The chemical structure scheme of flavonoids detected in petals of water lily.

<p>The chemical structure scheme of flavonoids detected in petals of water lily.</p

HPLC-DAD and HPLC-ESI-MS analysis of anthocyanins in water lily petals as well as the characterization and tentative identification.

1<p>: The bold numbers of compounds were reported for the first time in tropic water lily.</p