Eliciting increased flavonoids content in Ginkgo biloba leaves through exogenous salicylic acid and methyl jasmonate treatments

Prior to Ginkgo leaf harvest, we implemented four exogenous applications of salicylic acid (SA: 50, 80, and 100 mg * [L.sup.-1]) or methyl jasmonate (MJ: 20, 40, and 80 mg * [L.sup.-1]) as leaf spray to investigate their effect on flavonoids content and related enzyme activity. Compared with the control, a significant increase of 12% and 26% in flavonoid content was observed 7 days after the first application of 100 mg * [L.sup.-1] SA and 20 mg * [L.sup.-1] MJ, respectively; both were determined to be the best treatments. Operationally, administering either elicitor (SA or MJ) 1 week prior to leaf harvest is deemed to be the most practical and economic option. Additionally, enzymes activity involved in flavonoid metabolism (phenylalanine ammonialyase, cinnamate 4-hydroxylase, and 4-coumarate:coenzyme A ligase) and antioxidants (peroxidase, superoxide dismutase, and catalase) significantly increased in most SA and MJ treatments. The results strongly support Ginkgo leaf response to SA- or MJ-induced stress through increased nonenzymatic antioxidant compounds (flavonoids) and activity of antioxidant enzymes. Key words: Ginkgo leaves, flavonoids, antioxidant enzymes, salicylic acid, methyl jasmonate. Avant la recolte des feuilles de Ginkgo, nous avons procede a quatre vaporisations foliaires d'acide salicylique (AS : 50, 80 et 100 mg * [L.sup.-1]) ou de jasmonate de methyle (JM : 20, 40 et 80 mg * [L.sup.-1]) pour etudier leur effet sur la teneur en flavonoides et l'activite enzymatique associee. Comparativement au temoin, une augmentation significative de 12 et 26 % de la teneur en flavonoides a ete observee sept jours apres la premiere application de respectivement 100 mg * [L.sup.-1] de AS et 20 mg * [L.sup.-1] de JM; ces deux traitements etaient les meilleurs. De facon operationnelle, l'application de l'un ou l'autre des eliciteurs (AS ou JM) une semaine avant la recolte des feuilles est consideree comme l'option la plus pratique et la plus economique. De plus, l'activite des enzymes impliquees dans le metabolisme des flavonoides (phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, et 4-coumarate : CoA ligase) et des antioxydants (peroxydase, superoxyde dismutase et catalase) ont significativement augmente dans la plupart des traitements avec AS et JM. Les resultats concordent etroitement avec la reaction des feuilles de Ginkgo au stress induit par AS et JM par le biais de l'augmentation de la teneur en composes antioxydants (flavonoides) et de l'activite des enzymes antioxydantes. [Traduit par la Redaction] Mots-cles : feuilles de Ginkgo, flavonoides, enzymes antioxydantes, acide salicylique, jasmonate de methyle.
Introduction Ginkgo biloba L., commonly known as Ginkgo, is a native Chinese tree species whose leaves have been used in ancient traditional medicine. The medicinal applications of Ginkgo leaf extract [...]