Plant secondary metabolism and flower color changes in damask rose at different flowering development stages

Secondary metabolites content as well as petal color changes was quantified in flower extract of Rosa damascena Mill. during four flower development stages [(pre-anthesis; PA), (partially open flower; POF), (full open flower; FOF), and (senescent flower; SF)]. Petal brightness was increased at the last stage of flower opening compare to the PA level. An increase in b* value and decrease in a* value were recorded during damask rose flower development. The result of analysis by HPLC revealed that the main secondary metabolites of Rosa damascena Mill. flowers are phenolic acids [(gallic (GA), caffeic (CA), chlorogenic (CG), and coumaric (CO)] and flavonoids (rutin, quercetin, kaempferol, and apigenin). The content of most phenolic acids were the highest at SF stage, while the flavonoids content was the highest at FOF stage. The apigenin content was the highest at PA stage and then declined. Enzymatic activity of phenylalanine ammonia-lyase (PAL) showed a positive correlation with some flavonoids production. Results indicated that based on the need for specific phenolic compounds in the therapeutic process, flower harvesting at FOF stage or SF stage is suggested.