1. A compound represented by the following formula [I] or an optically active substance or a salt thereof:   (in the formula, a bond shown by a dotted line in the five-membered ring means that said five-membered ring may be any of a cyclopentene ring having a double bond and a cyclopentane ring where said bond is saturated and, in the case of a cyclopentene ring, X is OH, Y is =O and Z is H while, in the case of a cyclopentane ring, X is =O, Y is OH and Z is OH; R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 2. A compound or an optically active substance thereof or a salt thereof according to Claim 1 in which said compound is represented by the following formula [II]:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 3. A compound or an optically active substance or a salt thereof according to Claim 1 in which said compound is represented by the following formula [III]:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 4. A compound or an optically active substance thereof or a salt thereof according to any of Claims 1-3 in which R is thiol-containing aminoacid or derivative thereof. 5. A compound or an optically active substance thereof or a salt thereof according to Claim 4 in which the thiol-containing aminoacid is cysteine or glutathione. 6. A method for the manufacture of the compound represented by the formula [I] or an optically active substance thereof or a salt thereof:   (in the formula, a bond shown by a dotted line in the five-membered ring means that said five-membered ring may be any of a cyclopentene ring having a double bond and a cyclopentane ring where said bond is saturated and, in the case of a cyclopentene ring, X is OH, Y is =O and Z is H while, in the case of a cyclopentane ring, X is =O, Y is OH and Z is OH; R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). characterized in that 4,5-dihydroxy-2-cyclopenten-1-one represented by the formula [IV] or an optically active substance thereof or a salt thereof   is made to react with a thiol-containing aminoacid. 7. A method for the manufacture of a compound, an optically active substance thereof or a salt thereof according to Claim 6 in which the reaction is conducted under an acidic condition and the compound represented by the formula [I] is a compound represented by the following formula [II]:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 8. A method for the manufacture of a compound, an optically active substance thereof or a salt thereof according to Claim 6 in which the reaction is conducted under a neutral condition and the compound represented by the formula [I] is a compound represented by the following formula [III]:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 9. A method for the manufacture of a compound, an optically active substance thereof or a salt thereof according to any of Claims 6-8 in which R is thiol-containing aminoacid or derivative thereof. 10. A method for the manufacture of a compound, an optically active substance thereof or a salt thereof according to Claim 9 in which thiol-containing aminoacid is cysteine or glutathione. 11. A pharmaceutical agent which is characterized in containing at least one compound selected from a compound represented by the following formula [I] or an optically active substance thereof or a salt thereof as an effective component:   (in the formula, a bond shown by a dotted line in the five-membered ring means that said five-membered ring may be any of a cyclopentene ring having a double bond and a cyclopentane ring where said bond is saturated and, in the case of a cyclopentene ring, X is OH, Y is =O and Z is H while, in the case of a cyclopentane ring, X is =O, Y is OH and Z is OH; R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 12. A pharmaceutical agent according to Claim 11 in which said agent contains at least one compound represented by the following formula [II] or an optically active substance thereof or a salt thereof as an effective component:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 13. A pharmaceutical agent according to Claim 11 in which said agent contains at least one compound represented by the following formula [III] or an optically active substance thereof or a salt thereof as an effective component:   (in the formula, R is an aminoacid or peptide residue of corresponding thiol-containing aminoacid). 14. A pharmaceutical agent according to any of Claims 11-13 in which R is thiol-containing aminoacid or derivative thereof. 15. A pharmaceutical agent according to Claim 14 in which the thiol-containing aminoacid is cysteine or gutathione. 16. A pharmaceutical agent according to any of Claims 11-15 in which the agent is a biophylaxic agent, an agent for treating diabetes mellitus, agent for prevention diabetes mellitus, an anticancer agent, an apoptosis-inducing agent, agent which is against pathogenic microbes, an agent for treating hyperlipemia, agent for prevention hyperlipemia, agent for improvement of liver function, or heat shock protein-inducing agent. 17. A pharmaceutical agent according to Claim 16 in which the biophylaxic agent is selected from the group consisting of an antiallergic agent, an antirheumatic agent, antiphlogistic agent, prophylactic antiphlogistic agent, interferon inductor, tumour necrosis factor production inhibitor, prophylactic agent for prevention tumour necrosis factor production, interleucin-10 production stimulator, nitrogen monoxide production inhibitor, antigen Fas production inductor, immunomodulator, IgE production inhibitor, therapeutic agent for autoimmune diseases and delayed type anaphylacticy inhibitor. 18. A pharmaceutical agent according to Claim 16 in which the agent against pathogenic microbes is antibacterial or antiviral agent. 19. A pharmaceutical agent according to Claim 18 in which the antiviral agent is an antiviral agent in respect of immunodeficiency virus or virus of C type hepatitis. 20. A pharmaceutical agent according to Claims 18 in which the antiviral agent is an antiviral agent for human being, for non-human animals or for plants.