Study On Antioxidant And Antimicrobial Activity Of The Essential Oils And Extracts Of Elsholtzia Argyi Lévl. From Fujian Province

Elsholtzia argyi Levl. is an herbaceous, annual plant belonging to Lamiaceae family, which contains abundant essential oils. In folk medicine, E. argyi have been taken as remedies for the treatment of cold, fever and acute gastroenteritis. Modern research indicates that E. argyi can be used as phytoremediation for heavy metal-contaminated soils. In the view of full resource utilization, the main results of our study on E. argyi are summarized as follows:1.Analyzed by GC-MS, the result showed that the main volatile components of essential oils from wild and cultivated E. argyi were almost the same, includin-g 2,6-Octadienal,3,7-dimethyl-;(Z)-2,6-Octadienal,3,7-dimethyl-;Caryophyllene;(E)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl-; (Z)-1,3,6-Octatriene,3,7-dimethyl-;D-Limo-nene and so on. These components in the oil took up more than 70% of the tot-al contents, and most of them were terpenoid compounds with low boiling point. However, relative contents of the volatile components in the leaves and flowers fr-om wild and cultivated plants vary greatly, and the main components became diff-erent after they have been stored.In whole growth period, the amount of essential oils from cultivated E. argyi leaves was between 0.2% and 1.4%, and the variation was one-peak-curve. GC-MS analysis indicated that the major chemical components in the essential oils we re (E)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl- and Caryophyllene at the seedling s tage;the major components of essential oils in the fast growing stage were D-Li monene,2,6-Octadienal,3,7-dimethyl-; (Z)-1,3,6-Octatriene,3,7-dimethyl-;(Z)-2,6-Oc tadienal,3,7-dimethyl-; and (E)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl-.2,6-Octadie nal,3,7-dimethyl-; (Z)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl-; Caryophyllene; (Z)-2,6-Octadienal,3,7-dimethyl-and D-Limonene were the major components during th e blooming time. While 2,6-Octadienal,3,7-dimethyl; (Z)-1,3,6,10-Dodecatetraene,3, 7,11-trimethyl-;(Z)-2,6-Octadienal,3,7-dimethyl and Caryophyllene were the major components during the fruiting stage. We could see that the relative contents of th ese components in essential oils, such as (E)-1,3,6,10-Dodecatetraene,3,7,11-trimeth yl-; D-Limonene and 2,6-Octadienal,3,7-dimethyl- varied greatly from different har vest times. This indicated that the synthesis and accumulation of these components closely related to its growth cycle.Little essential oils were found in stem of E. argyi, and the main components were aliphatic compounds. The amount of essential oils in flowers was between 0.3% and 1.2%, and the main constituents were Caryophyllene; 2,6-Octadienal,3,7-dimethyl-; (E)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl-;and a-Caryophyllene. However, the relative contents of main components varied in the whole blooming time. Among all of them, the relative content of Caryophyllene reduced significantly from 25.35% to 7.14%, while the content of 2,6-Octadiena1,3,7-dimethyl kept increasing.The main components of leaf essential oils in white flower variation of E. argyi were (E)-1,3,6,10-Dodecatetraene,3,7,11-trimethyl-(26.30%), Caryophyllene(13.56%), 2,6-Octadiena1,3,7-dimethyl-(8.77%) etc, which took up about 53% of the total oil. These main constituents were almost consistent with the prototype of E. argyi, but the relative contents between them differed greatly.2. By Oxford-plate method, a preliminary study was carried out on the antibacterial activity of essential oils from leaves of E. argyi against seven tested strains (four species of bacteria and three species of fungal). The result showed that the essential oils had certain antibacterial effects on all the selected strains. The effects on Gram-positive bacteria(Bacillus subtilis and Staphylococcus aureus) were better than on others. The inhibitory effect on selected fungi was significantly stronger than that of yeast (p<0.05). The strength of antimicrobial activity may be related to semi-terpenes components of (E)-1,3,6,10-Dodecatetraene,3,7,1 1-trimethyl-; 2,6-Octadienal,3,7-dimethyl-; and caryophyllene of the essential oils.Using DPPH·method andβ-carotene bleaching, the vitro evaluation of antioxidant activity of the oil was carried out. The results showed that the essential oils had certain scavenging ability on DPPH·and anti-peroxidation effect. Compared with the synthetic antioxidants of BHT, the oil exhibited poor antioxidant effect in the above mentioned two different systems. It may be related to the lack of oxygenated terpene derivatives and other substances in the major components of the essential oils.3. Out of six kinds of macroporous resins tested, NKA resin was found having good ability of adsorption and desorption to polyphenols of E. argyi leaves. And then the factors affecting the adsorption-desporption process were researched. With NKA resin, polyphenols extracts from different organs of E. argyi were prepared by macroporous resin method. Using Folin-Ciocalteu method, the content of polyphenols extracts from four organs was determined, and the results showed that the root extract presented the highest content of polyphenols in four extracts, which was up to 463.73 mg·g-1, followed by the flower extract(369.80 mg·g-1), while that of stem extract and leaf extract were 307.69mg·g-1,302.89mg·g-1, respectively, between which there were no significant difference (p> 0.05).Antioxidant activities of polyphenols extracts were examined by 5 methods in vitro models. The result showed that polyphenols extracts from different organs of E. argyi had both strong reducing Ferric/antioxidant activity and strong scavenging abilities against artificial radicals (DPPH·and ABTS·+) and active oxygen radicals (O2-·and·OH). The root extract exhibited stronger scavenging abilities on DPPH·and O2-·, withρEC50 value were 0.115 mg·mL-1,0.052 mg·mL-1, respectively, and higher antioxidant activity in FRAP assay and TEAC method, with the TEAC value and FRAP value were 4.20 mmol TE·mg-1,8.06 mmol FeSO4·mg-1, respectively. Comparatively, the flower extract showed stronger·OH scavenging ability with theρEC50 value of 0.072 mg·mL-1. Compared with BHT and Rutin, which were used as positive controls, the scavenging capacity of controls and polyphenols from each organ against DPPH·ranks as follows:rutin>BHT>root> flower>stem>leaf, and the order of reducing Ferric/antioxidant activity were BHT≈root>stem>rutin≈flower> leaf. And that of scavenging abilitity on O2-·and·OH were rutin>root>flower>stem>leaf, flower>rutin>root>stem>leaf, respectively.Correlation analysis showed that antioxidant activity of E. argyi extracts was related to its polyphenol content, and indicated that the phenolic substances of extracts were the major contributor to their antioxidant activities.However, further studies on purification and identification of the above mentioned extracts are needed.In the view of resource utilization, apart from the great value of the essential oils in the leaves, phenolic substances and its antioxidant activity in E. argyr was also worth further consideration.