Hemijsko ispitivanje farmakološki aktivnih sekundarnih metabolita nekih vrsta roda Gentiana
Chemical investigation of pharmacologically active secondary metabolites of some Gentiana species
Abstract:
The genus Gentiana (Gentianaceae) comprises more then 400 species that are mostly distributed in the mountain regions of Europe, South America and Central Asia. There are 11 species of this genus growing in Serbia. Our study was focused on investigation of chemical constituents of G.dinarica (Beck), G.kochiana (Perr.et Song.), G. utriculosa L., G. lutea L., G.asclepiadea L., G.pneumonanthe L., G.verna L. and G.tergestina (Beck). Special attention has been paid to the research of G. dinarica, an endemic plant species. According to the literature data, it has not been phytochemicaly studied till now.
Some of the main subjects of this research are active pharmacological components of Gentiana species, such as secoiridoids, flavonoids and xanthones. One new and eighteen known compounds were isolated from plant material collected at natural localities using combination of extraction and chromatography methods. The isolated compounds were identified by means of spetroscopics techniques (UV, 1D NMR, 2D NMR and MS). They comprised 12 xanthones, where norswertianin-8-O-primeveroside appeared to be new compound, 4 C-glucoflavones and 3 secoiridoids.
- Xanthone glycosides with 1,3,7,8 –substitution pattern are prevalent components in investigated species. The oxygenation 1,3,7,8 –pattern of xanthone is characteristic for the genus Gentiana, particularly for the sections Calathianae and Megalanthe. Xanthone aglycones gentiakochianin (10) and gentiacaulein (11) were isolated from G. kochiana species, while xanthone primeveroside with 1,3,7 –substitution pattern was isolated from G. dinarica.
- According to distribution of isolated xanthone glycosides and aglycones, investigated species are divided into following sections:
Gentiana – G. lutea
Pneumonanthe – G. asclepiadea, G. pneumonanthe
Megalanthe – G. dinarica, G. kochiana
Calanthianae – G. utriculosa, G. verna, G.tergestina,
These results are in accordance with the previous hemotaxonomical research of Gentiana species.
- Beside C-glucoflavones isoorientin (6) and isovitexin (16) typical for Gentians, the presence of isoorientin-3’-O-glucoside was found in G. utriculosa and G. tergestina, and isoorientin-4’-O-glucoside (3) was found only in G. dinarica.
- As far as secoiridoid components are concerned, investigated species contain swerosid-type secoiridoids glucosides such as gentiopicrin and swertiamarin, and biphenyl secoiridoid amarogentin.
- Isolation of xanthone O-glycosides from the aerial parts of G. utriculosa has not been reported previously. Xanthone-C-glucoside lancerin (15) and 1,8-(OH)2-3-(OMe)-7-O-primveroside (17) are have been detected in this species for the first time.
- Our study was focused on research of chemical constituents of G. dinarica, an endemic plant species. Aerial parts were characterised by presence of secoiridoids and C-glucoflavones, while roots contain xanthone O-glycosides. It is important to point out that norswertianin-8-O-primeveroside has not been found in any plant species so far, and this is the first time that the compound of this structure has been detected.
In addition, we have examined potent antoxidant and antimicrobial activity of some plant extracts and isolated xanthone glycoside.
- It was shown that antiradical activity of xanthone compounds increased with the increaising number of OH groups.
- Presence of catechol groups and free OH groups at position 1 and 8 in the xanthone moleculs strongly enhance antiradical ability.
- Gentiakochianin (10) and norswertianin-1-O-primveroside (5) showed the best antiradical activity in comparison to other tested xanthones in 80 μM concentration.
- According to our results obtained on experimental model sistem such as bean weevil, norswertianin-1-O-primveroside has potent antioxidant activity only in adult males.
Antimicrobial activity of some plant extract and isolated xanthones were determined by bioautographic TLC metho and microdilution method.
- Only isoorientin (6) and isoorientin-4’-O-glucoside (3) showed antifungal activity against Candida albincans with minimal inhibitory concentration 25 μg/ml
- Butanolic root extract of G. dinarica showed the best antimicrobial activity against bacteria B. cereus, E. Coli, S. aureus and S. typhimurium