engleski

Natural sources of resveratrol and its derivatives

Oxidative stress, defined as « ; ; ; the imbalance between oxidants and antioxidants in favor of the oxidants potentially leading to damage» ; ; ; has been suggested as the cause of aging and various disease in humans. In modern western medicine, the balance between anti-oxidation and oxidation is believed to be the critical concept maintaining a healthy biological system. A general recommendation to the consumer is to increase the intake of foods rich in antioxidant compounds due to their well-known healthy effects. As a consequence these evidences accelerated the search for antioxidants principles, which led to the identification of natural resources and isolation of active antioxidant molecules. Resveratrol (3, 5, 4'-trihydroxystilbene) has emerged as one of the key molecules among bioactive phenols, due to its antioxidative, cardioprotective, antimutagenic, antiinflammatory, and especially emphasized, antitumor effect. Although resveratrol has been identified as active ingredient of some appreciated medicinal herbs, such as Polygonum cuspidatum, a plant with special position in traditional medicine of East, its content in our medicinal herbs has not been investigated. It can be supposed that some plants traditionally used in Croatian folk medicine are rich with resveratrol or its closely related conjugates and derivatives which also show biological activity and have potential therapeutic value. The results of screening of 70 medicinal plant extracts confirm that individual medicinal plants can be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea. The presence of free resveratrol monomers was confirmed in individual plant infusions prepared in common way in which teas are prepared for human consumption. During further investigations, extraction of phenolic compounds from plant material was conducted using alcoholic solvents. As the structure-activity relationship examination showed that glycosylation of the stilbenes could implicate with their biological properties, extraction was conducted under mild conditions to protect true structure of phenolic compounds. Polyphenolic composition and antioxidant properties of medicinal plant extracts were analyzed. The influence of the extraction mode on the efficiency of stilbene extraction was analyzed as well. Free radical scavenging ability and ferric reducing antioxidant power of plant extracts were compared at equal concentration value of total phenols. The separation and quantification of stilbenes by HPLC-RP-PAD indicated significant differences in the polyphenolic composition of selected plant extracts. Free resveratrol monomers, if found, were present in very small amounts, mostly as E-isomer. According to the obtained results it can be concluded that individual medicinal plants traditionally used in Croatian folk medicine can be an important source of polyphenolic compounds with high antioxidant capacity. Among plants comprised in this work, significant amounts of stilbenes were detected in Fragariae folium, Salviae folium, Teucrii montani herba and Menthae folium ethanolic extracts. The results of investigations strongly indicate that resveratrol or its hydroxy or methoxy derivatives are present in row plant material as glucosides. Resveratrol derivatives astringin, isorhapontin and/or piceid have been confirmed as dominant stilbenes in controlled medicinal plant extracts. The results of plant potential research, regarding the content of biologically active stilbenes, could motivate the development of new ways of using resveratrol-rich plant material, and find its application in the food industry (biologically valuable food production), as well as pharmaceutical industry.

stilbenes; resveratrol; natural sources

Sponsored by Alena Chemicals of Canada.