Alpinia officinarum, known as lesser galangal, is a plant in the ginger family, cultivated in Southeast Asia. It originated in China, where its name ultimately derives. It can grow several feet high, with long leaves and reddish-white flowers. The rhizomes, known as galangal, are valued for their spicy flavor and aromatic scent. The 80% aqueous acetone extract from the rhizomes of Alpiniaofficinarum, a Chinese medicinal herb, were found to inhibit melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. Among the constituents isolated, four diarylheptanoids [5-hydroxy-1,7-diphenyl-3-heptanone, 7-(4″-hydroxy-3″-methoxyphenyl)-1-phenylhept-4-en-3-one, 5-hydroxy-7-(4″-hydroxy-3″-methoxyphenyl)-1-phenyl-3-heptanone, and 3,5-dihydroxy-1,7-diphenylheptane] and two flavonol constituents (kaempferide and galangin) inhibited melanogenesis with IC50 values of 10–48 μM, and several structural requirements of the active constituents for the inhibition were clarified.