From the hypocotyl of scarlet runner bean (Phaseolus coccineus), a new 2,3-dihydro-2,5,-dihydroxy-6-methyl-4H-pyran-4-one conjugated saponin, named soyasaponin alpha a, was isolated together with two known saponins, soyasaponin alpha g and beta g. Their structures were elucidated by 1H NMR and 13C