Synthesis and antioxidant activity of hispolon, a yellow pigment from Inonotus hispidius †

steps, with an ove rall yi eld of 23 %. The spectral data of synthetic 5 are in agreement with those of natural S. Hispolon shows strong antio xid ant and weak antibacteri al activitie s. Hispolon 5 was isolated, recently, as yellow pigment from a parasitic fungus, Inonotus hispidius (Bull. Ex Fr.) Karst. (Basidiomycetes) during bioactivity guided isolation of the extract which showed immu­ nomodulatory and antiviral activity .l Due to our in­ terest on diarylheptanoids, 2-4 we have synthesised 5, for the first time and the results are reported in this paper. Knoevenagel-Doebner condensationS of veratral­ dehyde 1 with malonic acid gave 3,4-dimethoxycinnamic acid 2 in 80% yield. The reaction of 3,4dimethoxycinnamoyl chloride, prepared from 2, was treated with ethyl acetoacetate in the presence of NaH to give ethyl (4E)-2-acetyl-S-(3,4-dimethoxy ­ phenyl)-3-oxo-4-pentenoate 3 in 78 % yield. Decar­ boxylation of 3 using DMSO/NaCl 6 afforded 4hydroxy-6-(3,4-dimethoxyphenyl)-hexa-3,S-diene-2one 4 in 61 % yield. Demethylation of 4 using BBr/ gave the title compound 5 in 60% yield (Scheme I). The spectral data of synthetic 5 agree well with those reported for naturalS. Thus,S was obtained starting from veratraldehyde 1, in four steps with an overall yield of 23%. As caffeic acid and its derivatives show strong antioxidant activity, 8 and in view of structural similarity of 5 with caffeic acid derivatives, we ha ve screened 5 for antioxidant activity by the nitroblue tetrazolium (NBT) reduction method. 9 • lo 5 showed strong superoxide scavenging activity (ICso : 6 I-lg/mL) compared to other known antioxidants, vitamin E (ICso : >2000 I-lg/mL), BHT (butylated hydroxy toluene, ICso : 62 I-lg/mL) and BHA (butylated hydroxyanisole, ICso : 240 I-lg/mL). 4, in which no free hydroxyl groups are present on the aromatic ring, showed as anticipated 8 diminished antioxidant activity