Antinociceptive Constituents of Auricularia polytricha

As part of our project aimed to determine naturally occurring substances with antinociceptive properties, we have previously demonstrated that some triterpenoids present in Ganoderma lucidum (Leyss. ex Fr.) Karst. (Ganodermataceae), such as ganoderic acids A, B, G, and H, and compound C6 are the main active principles of this mushroom [1]. In this study, we have investigated the antinociceptive activity of the fruiting body of Auricularia polytricha (Mont.) Sacc. (Auriculariaceae).

Bioassay-guided fractionation, using the acetic acid-induced writhing method, of the CH₂Cl₂ extract of A. polytricha yielded three compounds (ceramide 1 and steroids 2 and 3), and of the MeOH extract yielded cerebroside 4 as antinociceptive components. The structures of compounds 1 - 4 were identified on the basis of comparison of their spectral and physical properties with those previously reported in the literatures [2], [3], [4], (copies of the original spectra are obtainable from the corresponding author). The antinociceptive activities of 1 - 4 were higher than that of the positive control (acetylsalicylic acid). As shown in Table [1], the activities of steroids (cerevisterol 2 and 9-hydroxycerevisterol 3) were higher than those of ceramide 1 and cerebroside 4. From the value of antinociceptive activities and yield (1 27.2 mg, 2 44.2 mg, 3 3.6 mg, 4 117.0 mg), cerevisterol 2 and cerebroside 4 contribute to the antinociceptive activity of A. polytricha. [*]

To clarify the active parts of the structures of 1 and 4, sphingosines (5 and 8) and fatty acids (6 and 9), prepared from 1 and 4, were examined in the bioassay. Sphingosines exhibited antinociceptive activity but the fatty acids did not. This indicates the sphingosine part to contribute to the antinociceptive activity of 1 and 4.

Table 1 Antinociceptive effects of ceramide (1), cerevisterol (2), 9α-hydroxycerevisterol (3), cerebroside (4), derivatives (5-9) and positive control (acetylsalicylic acid; ASA) on acetic acid-induced writhing in mice Compounds Dose (s.c.) inhibition (%) mg/kg μmol/kg 1 5 7.3 31.9 10 14.6 42.5* 20 29.3 49.6** 2 5 11.6 47.6* 10 23.3 60.9** 20 46.5 72.0** 3 5 11.2 55.7*** 10 22.4 68.2*** 4 10 13.2 38.2* 30 39.7 47.3* 5 5 15.8 35.7* 10 31.5 49.1*** 6 5 13.0 -6.9 10 26.0 0.0 7 10 16.9 32.7 20 33.7 41.3** 8 5 16.1 32.0 10 32.2 37.1* 9 5 16.7 17.4 10 33.3 14.7 ASA 30 166.7 22.2 50 277.8 41.8** 100 555.6 60.7** Values represent the mean of 5 - 6 experiments. Significantly different from the control value, *p < 0.05, **p < 0.01 and ***p < 0.001.

References

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• 2 Hung Q, Tezuka Y, Kikuchi T, Nishi A, Tubaki K. Studies on metabolites of mycoparasitic fungi. III. New sesquiterpene alcohol from Trichoderma koningii .  Chem. Pharm. Bull.. 1995;  43 1035-8
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• 4 Takaishi Y, Ohashi T, Murakami Y, Tomimatsu T. Investigation of the constituents of Inonotus mikadoi .  Bull. Inst. Chem. Res., Kyoto Univ.. 1987;  65 134-40