Iridoids extraction

Isol. from opulus iridoids extracted from the leaves of the ornamental shrub Viburnum opulus (common snowball). 

The solubility of iridoids depends on their state (free, glycosylated, acetylated), but usually they are extracted with polar solvents methanol, ethanol, aqueous alcohols, and rarely acetone. Iridoid glycosides are more or less stable some of them are very sensitive to acids and alkalis. Some iridoid glycosides such as aucubin suffer color modification after chemical or enzymatic hydrolysis they give first a blue to green... 

The family Hamamelidaceae consists of 26 genera and about 100 species of shrubs or tress known to contain tannins and iridoids. The leaves are alternate, simple, and often palmately lobed. The flowers are small and appear in spikes. The fruits are woody, capsular, and scepticidal. In Western medicine, the dried leaves of Hamamelis virginiana (hamamelis, British Pharmaceutical Codex, 1963), yielding not less that 20% of alcohol (45%)-soluble extractive, have been used as astringents for the treatment of hemorrhoids. Hamamelis water (British Pharmaceutical Codex, 1969) made from the stems has been used as a cooling application to sprains and bruises and as a styptic remedy. It is also used in cosmetics and as active ingredient of eye lotions. 

Table 2 illustrates the extraction methods and the iridoids isolated of some genera of Apoc3maceae. 

SPECIES / PLANT MATERIAL SOLVENT/ EXTRACTION METHOD ISOLATED IRIDOIDS REF. 

Table 2. Main extraction methodsto obtain iridoids of Apocynaceaefamily.

The bioassay-guided fractionation of the extracts of Plumeria rubra barks also proved to be a successful strategy, leading to the isolation of eleven substances, of which eight were iridoids. In this context, the aqueous extract of Plumeria rubra bark has iridoids such as the epimers, a-allamcidin and (l-allamcidin, which were resolved by preparative TLC on Si-gel G plates (20 x 20 cm, 250 pm, Merck ), using chloroform/ethyl acetate/methanol (3 3 1) as solvent system [44]. 

The methanol extract of the leaves of Cerhera manghas and its fruit contain the iridoids theve-side and theviridoside, as described in [124]. The methanol extract of the leaves, after the addition of water, was sequentially partitioned with chloroform, acetic acid and butanol. This extract and the aqueous phase were submitted to column chromatography with charcoal and water/ methanol as eluent. Theveside was isolated from the aqueous phase. Fractions of the butanol extract, which turn blue after heating with mineral acid, were chromatographed over a silica gel column with a gradient of increasing polarity of chloroform/methanol to afford theviridoside. 

The iridoids cerbinal, cerberic acid and cerberinic acid are found in the methanol extract of the bark of C. manghas [67]. The crude extract obtained by percolation from 4 kg of stem bark and 1.9 kg of root bark were diluted with water to 50% water methanol. The mixture was washed with hexane and partitioned with benzene. Benzene fractions were re-suspended in methanol and cerbinal (120 mg from stem bark extract and 300 mg from root bark extract) precipitated. 

According to [44] the iridoids fulvoplumierin, allamandin, a- and jl-allamcidin, plumieride, 15-demethylplumieride, 13-O-trflMS-p-coumaroylplumieride and plumericin are present in extracts of Plumeria rubra. For isolation of these iridoids, the stem bark (2.5 kg) was successively extracted with petroleum ether and methanol followed by bioguided fractionation to investi-... 

The iridoids, plumericin, isoplumericin, plumieride and fulvoplumierin, were present in the extracts of Plumeria rubra bark. After maceration of the powdered bark (3.5 kg) with dichloro-methane/methanol (1 1) and pure methanol, the combined extracts were partitioned between water and ethyl acetate. To isolate the four iridoids, the organic layer was chromatographed twice in a column using silica gel and gradient of increasing polarity with hexane and ethyl acetate, ethyl acetate and methanol, and then pure methanol. The amounts of the compounds isolated were not reported [75]. 

Isoplumericin and plumericin are present in the bark of Himatanthus sucuuba [88]. For the isolahon of these iridoids, 95% ethanol extract (2 g), obtained from 50 g of plant material was submitted to column chromatography using silica gel and gradients of increasing polarihes with hexane, ethyl acetate and methanol. After recrystallizahon, isoplumericin (18 mg) was obtained from ethyl acetate and plumericin (70 mg) from methanol. 

The iridoids, scholarein A, B, C and D, can be obtained by the fractionation of the ethanol exhact horn bark ofAlstonia scholaris [60]. The crude extract, obtained from 15 kg of the plant material, was parhhoned between ethyl acetate and water. The organic layer (190 g) was... 

Studies on HPLC with iridoids of Apoc)maceae focus mainly on the separation of components from extracts or fraction. The chromatography profile, the identification and quantification of these terpenes in the extracts are described. Table 4 shows the principal references on iridoids isolated from Apoc)maceae by HPLC, MPLC and LPLC. 

Valerian is used in the treatment of insomnia and stress and anxiety. The important active compounds of valerian are the valepotriates (iridoid molecules) and valeric acid. These compounds are found exclusively in valerian. Originally, it was thought that just the valepotriates were responsible for valerian s sedative effects but, recently, an aqueous extract of valerian has also been shown to have a sedative effect. As the valepotriates are not soluble in water, it was concluded that valeric acid also possesses sedative action and is the chemical factor responsible for the sedative effect noted in human clinical trials with aqueous extracts of valerian (Murray, 1995). Valerian inhibits the uptake of GABA and enhances the release of GABA. 

Note Valerian consists of the dried rhizome and roots of Valeriana officinalis Linne (Fam. Valerianaceae). It has been employed as an antianxiety agent and sleep aid for more than 1000 years. The drug contains from 0.3 to 0.7% of an unpleasant-smelling volatile oil containing bornyl acetate and the sesquiterpenoids, valerenic acid, and acetoxyvalerenolic acid. Also present is a mixture of lipophilic iridoid principles known as valepotriates. These bicyclic monoterpenoids are quite unstable and occur only in the fresh plant or in material dried at temperatures under 40°C. Although the specific active principals of valerian have not been determined, it is possible that a combination of the sesquiterpenoids and the valepotriates may be involved. The drug may be administered as a tea prepared from 2 to 3 g of the dried herb or equivalent amounts of a tincture or extract may be employed. 

Rischer, M. Adamczyk, M. Ratz, H. Hose, H. Marchsan, M. Paper, D.H. Franz, G. Wolf-Heuss, E. Engel, J. Quantitative determination of the iridoid glycosides and catapol in Plantago Lanceolate L. extracts by HPTLC and HPLC. J. Planar Chromatogr.-Mod. TEC 1998, 11, 374-378. 

Thirty-three known iridoid and secoiridoid glucosides have been analysed by gas chromatography of their trimethylsilyl derivatives. G.c.-m.s. analysis of several representative compounds e.g. 4-CO2H, 4-C02Me, 4-unsubstituted) demonstrated the feasibility of iridoid-containing plant extract analysis and resulted in the identification of secologanoside 11-methyl ester (99 R = H, X = CH2) from Lonicera morrowii the sixth paper in a series of chemotaxonomic studies on iridoids illustrates the need for accurate analysis of minor components. ... 

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