(1'RS,2'SR,6'RS)-(2,6-Dihydroxy-4-methoxyphenyl)-[3'-methyl-2'-(3''-methylbut-2''-enyl)-6'-phenyl-cyclohex-3'-enyl]methanone (panduratin A)-a Constituent of the Red Rhizomers of a variety of Boesenbergia pandurata