作者
S. Venkateswarlu,Marellapudi S. Ramachandra,K. Sethuramu,Gottumukkala V. Subbaraju
摘要
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