herbalbin nitrosin herbalbin grácil in grácil in
1 -oxo-cryptomeridiol o artemisinin rotundopontilide of A. pontica rotundopontilide of A. pontica
Figure 3 Structural formulae of some representative sesquiterpene lactones found in the genus Artemisia.
oh o apigenín och3
quercetin kaempferol rhamnazln quercetin kaempferol rhamnazln
was found to be active in inhibiting some cytophysiological activities of the parasite (Yang et al., 1995). In African species of Artemisia (reviewed by Saleh and Mosharrafa 1996), apigenin was found in aerial parts of A. mesatlantica, and its 7-methyl ester in A. afra. Acacetin, jacoesidin, cirsilineol, cirsimaritin (Fig. 4), hispidulin, isoschaftoside, lucenin-2 and vicenin-2 were all isolated from A. judaica, A. monosperma and A. herba-alba. Pectolinarigenin and salvigenin (Fig. 4), were extracted from A. santolina, luteolin from A. afra, chrysoeriol from A. mesatlantica, nepetin from A. afra, cirsiliol from A. campestris, eupatilin from A. judaica, tricin from A. mesatlantica, and an acerosin derivative from A. herba-alba. Aerial parts of A. monosperma contained acacetin-7-glycoside, whereas luteolin-3'-glycoside was found in A. judaica. Isovitexin was isolated from A. herba-alba, whereas neoschafto-side and neoisoschaftoside were extracted from A. judaica. The flavonols kumatak-enin, axillarin and casticin were isolated from A. campestris, A. afra and A. judaica, respectively, whereas quercetin-5-glycoside, isorhamnetin 5-glycoside and patuletin-3-glycoside were extracted from A. monosperma, A. judaica and A. herba-alba (Saleh and Mosharrafa 1996).
The flavonoids mentioned above may occur both as O-glycosides and as methylated flavones and flavonols. Methylated flavones have been detected in A. arctica ssp. saxicola and A. herba-alba, whilst methylated flavonols have been identified in A. arbuscula, A. tridentata, A. rothrockii, A. cana, A. absinthium, A. longiloba and A. arborescens (Greger 1977).
Flavonoid components of 130 species of Artemisia have been used for the solution of taxonomic problems at the intrageneric level. By considering three sections (Artemisia, Abrotanum and Absinthium) and two subgenera (Seriphidium and Dracunculus), Belenovskaja (1996) was able to distinguish several groups of species according to the flavonoid composition: a) section Artemisia, two groups, one containing quercetin and isorhamnetin and the other 6-methoxyluteolin methylesters; b) section Abrotanum, several groups of species containing mainly common flavonols (quercetin, kaempferol, etc.), their O-glycosides, 6-methoxyluteolin, 6-methoxy-quercetin derivatives and coumarins; c) section Absinthium, two groups, one with methylethers of flavonols and the other with methylethers of flavones; d) subgenus Seriphidium, quite similar patterns of distribution when compared to the genus Artemisia-, e) subgenus Dracunculus, completely different from the other subgenera of Artemisia with flavanones with an unusual type of distribution.
Several species of Artemisia were analysed for their leaf exudate flavone and flavonol aglycone content and the majority of these compounds were 6-methoxy-lated, with additional substitutions at the 7-, 3'- and 4' position along with some coumarin derivatives (Valant-Vetschera and Wollenweber 1995). Finally, four flavonols with spasmolytic activity were isolated from A. abrotanum (Bergendorff and Sterner 1995), whereas several other flavonoids have been extracted from A. austriaca (Cubukcu and Melikoglu 1995) and from other Artemisia species (Al-Hazim and Basha 1991).
Hydroxycoumarins are typical constituents of the genus Artemisia representing a valuable chemotaxonomic character. Structurally complex coumarins such as scopoletin 7-dimethylallylether and methylene ethers of daphnetin and fraxetin have been isolated in A. dracunculoides (Herz et al., 1970), whereas in A. afra root extracts contained isofraxidin while flowers contained scopoletin (Fig. 4) (Bohlmann and Zdero 1972). Esculetin (Fig. 4), isoscopoletin and their 7-O-glycosides esculin and methyl-esculin were isolated from A. tridentata ssp. vaseyana (Shafizadeh and Melnikoff 1970), while p-hydroxyacetophenone, herniarin, scoparone, scopoletin, umbelliferone and dehydrofalcari-3,8-diol were extracted from A. marschalliana (Ozhatay and Cubucku 1990). Tissue cultures of A. vulgaris produced significant amounts of the 6,7,8-trioxygenated coumarin isofraxidin, whereas A. laciniata was found to contain the chiral glycol of the trioxygenated isofraxetin (Murray 1995).
So far, the evaluation of more than 550 species belonging to 11 plant families has proved that plant surface wax alkanes can be considered good chemotaxonomic markers at the familial, subfamilial and tribal level (Maffei 1994; 1996a; 1996b; 1996c; Maffei et al., 1993b; 1997). This is mainly due to the universality of the occurrence of these molecules, species variation in composition, simplicity of sampling, and availability of rapid analytical tools.
The leaf-wax alkane profiles of some Artemisia species revealed the presence of odd and even carbon number alkanes as well as branched molecules (Maffei 1996c) (Table 5). The highest total alkane content was found for A. siversiana and A. absinthium, whereas the lowest contents were present in A. abrotanum and A. pontica. The alkane carbon chain-length ranged from C23 to C33. The main components in all species were C29 and C31, with A. pontica containing the highest percentage of the former and A. vulgaris of the latter compound. A. alba also contained high percentages of the branched alkane 2MC28. The common occurrence in Angiosperms of C29 and C31 has been documented by a large number of reports and the presence of zso-alkanes has been demonstrated in several plant waxes (Maffei 1994 and refs. cited therein).
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