From Teucrium species

According to Rowe s nomenclature [14], the hydrogen at C-lOa being and methyl at C-5 P(Me-19) indicate clerodane, the reverse en/-clerodane structure. Roger [ 15] assigned en/-/jeo-clerodane for the former and neo-clerodane for the latter type of stmctures. In the present day, clerodane and neo-clerodane names are used commonly. Most of the diterpenoids isolated from Teucrium species have neo-clerodane structures. 

Triterpenic and steroidal compounds were also isolated from Teucrium species. Common triterpenic acids such as ursolic acid, oleanolic acid and small amounts of micromeric acid were isolated from T.fruticans [81] while a-amyrin, lupeol, sitosterol and stigmasterol were present in T. divaricatum subsp. villosum [75]. Two new steroidal compounds SP-hydroxy-stigmast-24(24i), 25-dien-242-al (157) and 3P-hydroxy-24a-ethylcholesta-5, 25-dien-7-one (158) were isolated together with two known compounds 24a-ethylcholesta-5, 25-dien-3P-ol (159) and sitosterol from the aerial parts of T.chamaedrys subsp. chamaedrys [82]. The plant also yielded a-amyrin and ursolic acid. The structures of the new steroidal compounds were established by NMR techniques and by comparison of similar known compounds (Table 24). 

Diterpenes of this series are formed by rearrangement of the labdane skeleton during cyclization (Hanson, 1991 West, 1981) (Fig. 22.11). Many highly oxygenated diterpenes of this series are found in the Lamiaceae and Verbena-ceae. There are over 400 known clerodanes many of these are from Teucrium species (Lamiaceae) (Hanson, 1991). 

Although the absolute configuration of these clerodanes from Croton species was not determined, the absolute stereochemistry of a number of clerodanes from Teucrium (Labiatae) species has been clarified.39 19-Acetylgnaphalin and iso-fruticolone were shown to belong to the neoclerodane series. Teuflin (24) has been obtained40 from Teucrium viscidum and details of an X-ray structure have been published.41 The structure (25), without absolute configuration, was assigned42 to... 

The eo-clerodane diterpenoids were isolated from the aerial parts of Teucrium species, however, from the roots rearranged abietane diterpenes were obtained. The first study with the roots of T. polium subsp. vincentinum was carried out by the Spanish-Italian group [71]. In this study four new compounds teuvincenones A, B, C and D (122-125) have been isolated. Two of them, teuvincenones C (124) and D (125) possess a novel hydrocarbon skeleton which contains a cyclopropane ring constituted by C-3, C-4 and C-18 carbons of the 17(15-16)-a6eo-abietane framework. 

From the aerial parts of Teucrium species flavonoids have been also isolated, although they are not abundant. Luteolin was obtained from T. scorodonia [26], salvigenin from T. flavum [65], salvigenin, circimaritin from T. massiliense [55], luteolin, luteolin 7-0-glucoside and 6-... 

The quantitative composition of the essential oils from six Teucrium species collected from Iberian peninsula have been studied and sixty two constituents have been identified. Five populations of T. scorodonia subsp. scorodonia, three populations of T. scorodonia subsp. baeticum, two samples of T. oxylepis subsp. marianum and several samples of T. asiaticum, T. salviastrum and T. oxylepis subsp. oxylepis were studied and no significant differences were found in the terpenoid (monoterpenes and diterpenes) patterns. The GC columns were packed with 5 % silicon OVl and 10 % carbowax 20M [91]. 

Teucrium species are used in folk medicine as diuretic, diaphoretic, carminative, astringent, stimulant and tonic, antiseptic, antipyretic and antiinflammatory agents. T. cubense [92] for example is used against stomach aches and as an amoebacide. Teucjaponin A(32) obtained from T. japonicum [33] was shown to be antifeedant for the larve of Prodenia litura. Its threshold concentration for inhibitory activity was about 400 ppm in the leaf disk test. Generally neo-clerodane diterpenes posses insect antifeedant activity and they are used as antifungal, antitumor and antibacterial agents [56,63]. The antitumor activity of T. bicolor [52] was reported. The antifeedant activity of neoclerodanes is mentioned in a... 

In later years from a Spanish species of Teucrium, T. carolipaui C. Vicioso ex Pan [77]. which grows only in small areas of south-east Spain, a new sesquiterpene 11-hydroxy-valenc-l(10)-en-2-one (142) was isolated and its structure was determined by NMR techniques (Table 22). Three new guaiane sesquiterpenoids, teucladiol (143), teuclatriol (144) and 10-epiteuclatriol (145) were isolated from the aerial parts of T. leucocladum [78] and their structures were established spectroscopically (Table 22). 

Three 24-ethylcholestane derivatives v ere isolated from t>vo species of Teucrium, T. abutiloides and T. betonicum [83]. All of this compounds have 24P-configuration and identified as (24S)-24-ethyl- cholesta-5,22(E), 25-trien-3P-ol (160), (24S)-24-ethylcholesta-5, 25-dien-3P-ol(clerosterol)... 

Clerodanes.—The reversal of the absolute configuration assigned to clerodin has led to some controversy over that assigned to the ajugarins. They now appear to have the neo-clerodane absolute stereochemistry. Teucrium (Labiatae) species have continued to be a source of new clerodanes. Eriocephalin, isolated from T. eriocephalum, was assigned the structure (24) on the basis of an X-ray analysis and the structure (25) has been assigned to a clerodane from T. polium. 

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