Analysis of aroma components in water lilies of different subgenera by HS-SPME-GC-MS

【Objective】 This study aimed to analyze the types and contents of aromatic components in water lilies of different subgenera， and clarify the aroma differences and primary fragrance-imparting substances among them， providing a reference for screening excellent fragrant water lily cultivars and breeding new cultivars with different aromas.【Method】 Headspace solid phase microextraction （HS-SPME） with gas chromatography-mass spectrometry （GC-MS） was employed to determine the volatile components in ten water lily cultivars： Pigeon Blood and Jakkaphong （Nymphaea）； Red Flare and Thai Pink （Lotos）； Nymphaea prolifera Wiersema and Nymphaea rudgeana （Hydrocallis）； Wanqiu and Purple Shell （Anecphya）； and Nymphaea micrantha and Purple Joy （Brachyceras）. The relative contents of volatile components were calculated using the internal standard method. An orthogonal partial least squares discriminant analysis （OPLS-DA） model was established to perform variable importance in projection （VIP） analysis for screening differential metabolites.【Result】 A total of 83 volatile components were identified across the ten water lily cultivars， which were mainly classified into seven compound classes： alkanes， terpenes， esters， alcohols， ethers， aldehydes， and ketones. The top three compound classes by proportion were alkanes， ethers， and terpenes， accounting for 45.14%， 40.32%， and 11.20%， respectively. The total content of volatile components in the ten water lily cultivars was ranked as follows： Nymphaea prolifera Wiersema （73.170 μg/g）>Nymphaea micrantha （40.809 μg/g）>Wanqiu （25.963 μg/g）>Purple Shell （24.119 μg/g）>Pigeon Blood （11.021 μg/g）>Thai Pink （7.592 μg/g）>Red Flare （4.436 μg/g）>Purple Joy （1.719 μg/g）>Jakkaphong （0.908 μg/g）>Nymphaea rudgeana （0.224 μg/g）， with their corresponding numbers of detected volatile components were 20， 31， 43， 46， 33， 32， 25， 33， 33， and 15， respectively. The compound richness was the highest in Anecphya， followed by Brachyceras， and the lowest was in Hydrocallis. Cluster analysis results revealed that cultivars of Nymphaea， Lotos， and Hydrocallis clustered together， while cultivars of Anecphya and Brachyceras formed another cluster， and cultivars of the same subgenus clustered in pairs. Fourteen differential metabolites were screened from the 83 volatile components （P<0.05）， including five alkanes， six terpenes， one ether， one alcohol， and one ester. Among them， four aroma substances （tridecane， tetradecane， pentadecane， and anisole） were shared components across all ten water lily cultivars. Two aroma substances， （3R-trans）-6-methyl-1-（3-methylvinyl） cyclohexene and isopropyl isothiocyanate， were identified as specific components of Lotos.【Conclusion】 Differences in classes and contents of aroma components lead to different aroma profiles among water lily cultivars of different subgenera. The characteristic aroma components of different subgenera can provide a basis for classification of subgenera. Cultivars of Anecphya and Brachyceras are rich in aroma components， indicating strong potential for development into cosmetics or highly fragrant cut flowers.