Chemical Constituents Of Cordyceps

The chemical composition of C. sinensis, first described in 1947 (4), includes 25% crude protein, 8.4% fat, 18.5% crude fiber, 29% carbohydrate, and 4.1% ash. In 1957, cordycepic acid, which was identified as D-mannitol, was isolated from C. sinensis, and subsequently it has been used as a marker of quality control of Cordyceps for a number of years (21). In 1964, 3'-deoxyadenosine, namely cordycepin, was isolated from cultured Cordyceps militaris (4), a related species of C. sinensis commonly used as a substitute; however, its existence in C. sinensis is controversial. To date, cordycepin has never been identified from C. sinensis. In 1981, uracil, adenine, adenosine, trehalose, mannitol, ergosterol, and stearic acid were identified from C. sinensis (22). At present, C. sinensis is known to contain steroids, nucleosides, carbohydrates, and amino acids.

Sterols and their derivatives have been isolated from natural and cultured Cordyceps. They are ergosterol, D3 ergosterol, ergosterol peroxide, ergosteryl-3-O-h-D-glucopyranoside, 22,23-dihydroergosteryl-3-O-h-D-glu-copyranoside, h-sitosterol, daucosterol, cholesterol, cholesteryl palmitate, campesterol, and dihydrobrassicasterol. Based on the activity-guided fractionation, two antitumor compounds, 5a, 8a-epidioxy-24(R)-methylcho-lesta-6,22-dien-3 h-D-glucopyranoside and 5,6-epoxy-24(R)-methylcholesta-7,22-dien-3|h-ol (Fig. 5), were isolated from the methanol extract of C. sinensis (23). H1-A (Fig. 5), which suppresses the activated human mesangial cells and alleviates immunoglobulin A nephropathy (Berger's disease) with clinical and histological improvement, is a purified compound from the fruiting body of C. sinensis (24).

Nucleosides in Cordyceps have been a focus since the isolation of cordycepin from cultured C. militaris, which was shown to have antitumor activity. More than 10 nucleosides and related compounds have been isolated from Cordyceps, including adenine, adenosine, uracil, uridine, guanidine,

Figure 5 Structures of sterols and nucleoside isolated from Cordyceps. (1) 5a, 8a-Epidioxy-24(R)- methylcholesta-6,22-dien-3|-D-glucopyranoside; (2) 5,6-epoxy-24(R)-methylcholesta-7,22-dien-3|-ol; (3) H1-A; (4) N6-(2-hydroxy-ethyl)-adenosine.

Figure 5 Structures of sterols and nucleoside isolated from Cordyceps. (1) 5a, 8a-Epidioxy-24(R)- methylcholesta-6,22-dien-3|-D-glucopyranoside; (2) 5,6-epoxy-24(R)-methylcholesta-7,22-dien-3|-ol; (3) H1-A; (4) N6-(2-hydroxy-ethyl)-adenosine.

OH OH

OH OH

guanosine, hypoxanthin, inosine, thymine, thymidine, and deoxyuridine (25,26). In addition, N6-(2-hydroxyethyl)- adenosine (Fig. 5), which behaves as a Ca2+ antagonist and an ionotropic agent, was isolated from cultured mycelia of Cordyceps (27).

D-Mannitol is one of the major compounds in natural Cordyceps, and contributes over 3.4% of the total dry weight (28). Cordyceps contains a large amount of polysaccharides, ranging from 3 to 8% of the total dry weight (29). A water-soluble, protein-containing galactomannan was isolated from the sodium carbonate extract of Cordyceps, and its molecular weight was estimated by gel filtration to be ~23 kDa. The isolated compound was composed of D-mannose and D-galactose in a molar ratio of 3:5, and contained a small proportion of protein. It is a highly branched structure composed of (1^6)-and (1^2)-linked a-D-mannopyranosyl residues in the main chain (30). Another polysaccharide with hypoglycemic activity, purified from a hot-water extract of the cultured mycelium of C. sinensis, was a combination of galactose, glucose, and mannose in a molar ratio of 43:33:24; its molecular weight was estimated to be about 15 kDa. The results of chemical and spectroscopic investigations suggest that the polysaccharide has a comb-type structure (31).

More than 20% of amino acid is found in Cordyceps, which could be responsible for its tonic and immunopotentiating activity (32). Six cyclo-dipeptides were isolated from cultured Cordyceps, and one of them, cyclo-(L-glycyl-L-prolyl), had antitumor and immunopotentiation activity (33).

In addition, Cordyceps contains about 0.18% dry weight of phospho-lipid, including eight phospholipids; the major constituents are phosphati-dylcholine, phophatidylinositol, phosphatidylserine, phosphatidylethanol-amine, and phosphatidic acid (34). Some organic acids, such as palmitic acid, stearic acid, oleic acid, and linoleic acid, and vitamin B12 and C were also identified in Cordyceps.

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