Comparative Analysis of Essential Oil Components and Antioxidant Activity of Extracts of Nelumbo nucifera from Various Areas of China

This study was designed to examine the composition of extracts and essential oil components from Nelumbo nucifera leaves from the principal habitats in China. The amounts of phenolics, flavonoids, and proanthocyanidins in the lotus leaf extracts varied widely, ranging from 354 to 487 mg/g gallic acid equivalents, from 172 to 236 mg/g rutin equivalents, and from 124 to 179 mg/g catechin equivalents, respectively. All of the extracts had strong antioxidant activity in comparison to the standard compounds butylated hydroxytoluene and vitamin C. Wild lotus samples from Baiyangdian Lake and Weishan Lake exhibited a stronger free radical scavenging effect and greater reducing power than the Cultural samples, but no such differences were observed in the inhibition of lipid oxidation. Chemical variation in the essential oils from the various samples was analyzed by GC-MS. The main constituents were l-(+)-ascorbic acid 2,6-dihexadecanoate (0-33.5%), trans-phytol (5.1-24.1%), hexahydrofarnesyl acetone (5.6-15.3%), pentadecyl acrylate (2.2-12.4%), geranyl acetone (1.9-8.0%), and beta-ionone (0-8.0%). The rhizome lotus and seed lotus samples were clustered into separate groups by hierarchical cluster analysis according to the composition of the corresponding essential oils. No significant relationship was found between essential oil composition and geographical distribution of the 11 populations. However, the results indicated that region of origin and growing conditions could significantly affect both the bioactivities of the lotus leaf and the content of bioactive compounds in the leaves. Thus, the existence of chemical polymorphism in the N. nucifera leaf in China was demonstrated.