The Flavonoids Compostion In Herbaceous Peony Petals And Their Effects On The Coloration

Herbaceous peony,a perennial herb flower of section Paeonia,genus Paeonia,the family Paeoniaceae,is a traditional ornamental and medicinal plant in China.The pigments composition among one species,i.e.Paeonia lactiflora and 138 cultivars were subsequently analyzed qualitatively and quantitatively by the high-performance liquid chromatography coupled with diode array detection(HPLC-DAD)and HPLC with electrospray ionization mass spectrometry(HPLC-ESi-MS2).The differences of flavonoids composition among them were explored.Then,the effects of flavonoids on the petal coloration were discussed.The main results were as follows.1.The diversity of floral colors in herbaceous peony petalsThe floral colors were measured by the Royal Horticultural Society Colour Chart(R.H.S.C.C.),and they change from yellow(4C)to red purple(79C).The system of CIEL*a*b*displayed that the value of a*-value changed from-10.00 to 64.03 while b*-value was from-25.32 to 22.30.There is a negative relationship between a and b.The floral colors were classified into six clusters according to the L*,a*,b*values by hierarchical cluster analysis and they were white,pink,pinkish-purple,red-purple,red and yellow.2.Identification of anthocyanins and flavonols in herbaceous peony petalsA fast and reliable HPLC method was developed for simultaneous separation of anthocyanins and flavonols in herbaceous peony petals by optimizing analytical parameters,including the solvent system,flow rate,temperature and elution gradient etc.Forty-seven flavonoids,including 11 anthocyanins,30 flavonol glycosides,four flavone glycosides,one chalcone glucoside and one flavanone,were characterized according to the standards and authentic samples or tentatively identified by using HPLC-MS2.Among them,38 flavonoids were reported for the first time in the petals of herbaceous peony.They were five anthocyanins:cyanidin-3-O-galloyl glucoside(Cy3GloG),peonidin-3-O-galloyl glucoside(Pn3GloG),peonidin-3-O-galloyl glucoside-5-O-glucoside(Pn3GloG5G),peonidin-3-O-malonyl glucoside-5-O-glucoside(Pn3GloG5G),peonidin-3-O-galloyl glucoside-5-O-galactoside(Pn3GloG5Gal);28 flavonol glycosides:quercetin-7-O-glucoside(Qu7G),quercetin-3-O-malonyl glucoside-7-O-glucoside(Qu3MloG7G),quercetin-3-O-glucoside(Qu3G),quercetin-3-O-galloyl glucoside(Qu3G1oG),quercetin-3-O-arabinoside(Qu3Ara),quercetin-3,7-di-O-glucoside(Qu3G7G),quercetin-3-0-glucoside-7-0-arabinoside(Qu3G7Ara),Myricetin-3,7-di-O-glucoside(My3G7G),kaempferol-7-O-glucoside(Km7G),kaempferol-3-O-malonyl glucoside-7-O-glucoside(Km3MloG7G),kaempferol-3-O-malonyl glucoside(Km3MloG),kaempferol-3-0-glucoside-7-O-arabinoside(Km3G7Ara),kaempferol-3-O-galloyl glucoside(Km3GloG),kaempferol-3-O-arabinoside-7-O-glucoside(Km3Ara7G),kaempferol-3-O-arabinoside(Km3Ara),kaempferol-3-O-arabinoside(chalcone2'G),kaempferol-3,7-hexoside(Km3,7-di-hexoside),Isorhamnetin-7-O-arabinoside(Is7Ara),Isorhamnetin-3-O-malonyl glucoside-7-O-glucoside(Is3MloG7G),Isorhamnetin-3-O-glucoside-arabinoside(Is3GAra),Isorhamnetin-3-O-glucoside-7-O-arabinoside(Is3G7Ara),Isorhamnetin-3-O-glucoside(Is3G),Isorhamnetin-3-O-galloyl glucoside(Is3GloG),Isorhamnetin-3-O-galactoside(Is3Gal),Isorhamnetin-3-O-arabinoside(Is3Ara),Isorhamnetin-3,7-di-0-glucoside(Is3G7G);four flavone glycosides:luteolin-7-O-galloyl glucoside(Lu7GloG),luteolin-7-O-arabinoside(Lu7Ara),luteolin-5-O-glucoside-7-O-rhamnoside or luteolin-5-O-rhamnoside-7-O-glucoside(Lu5G7Rha or Lu5Rha7G),luteolin-5-O-malonyl glucoside-7-O-rhamnoside or luteolin-5-O-rhamnoside-7-O-malonyl glucoside(Lu5GloG7Rha or Lu5Rha7GloG)and one flavanone glycoside:Eriodictyol-7-O-glucoside(Er7G).3.The Changes of Floral Color and Pigments Composition During the Flowering Period in Paeonia lactiflora Pallasduring the blooming period,the floral lightness increased while the value of chroma decreased?The multiple linear regression analysis showed that the contents of Pn3G5G,Isorhamnetin-3-O-glucoside,quercetin-3-O-glucoside,quercetin-7-O-glucoside were linear correlation with the floral color changing.4.The characteristics of pigments composition in herbaceous peony petalsThe differences among cultivars were significant in the composition and content of flavonoids.Especially,the differences were mainly focused on the anthocyanins content among the cultivars with different colors.Most white and yellow cultivars didn't contain anthocyanins or traces of Pn3G5G.Pinkish-purple cultivars just contained Pn3G5G or a small amount of Cy3G5G at the same time.In pink cultivars,there were only Pn3G5G and Cy3G5G.But there were more than five anthocyanins found in red-purple cultivars.Therefore,Pn3G5G was the most dominant pigment in all species and cultivars.What's more,chalcone played a critical role in yellow cultivars,and the major anthoxanthins in herbaceous peony petals were Km3G7G and Km3G.5.The metabolic pathway of flavonoids in herbaceous peony petalsThe metabolic pathway of flavonoids in the herbaceous peony petals was inferred according to the final products detected.The pathway began with the synthesis of 4,2',4'.6'-tetrahydroxychalcone(THC)from 4-coumaroyl CoA and malonyl CoA.On one hand,THC was glucosylated to chalcononaringenin-2'-O-glucoside.On the other hand it was isomerized to naringenin,which was catalyzed by a series of enzymes.In total,nine flavonoid aglycones(eriodictyol,quercetin,myricetin,kaempferol,isorhamnetin,luteolin,cyanidin,peonidin,pelargonidin)were synthesized and then changed into flavonoid glycosides after glycosylation and acylation.This study investigated the diversity of floral colors and pigments composition in herbaceous peony petals and then elucidated the probable metabolic pathways of flavonoids.It was helpful to provide guidelines for breeding new cultivars with novel colors and developing sorting method according to pigments composition.It would also contribute to the further study and utilization of herbaceous peony flowers.