A new menaquinone homologue was isolated from a nocardioform bacterium, Actinomadura madurae. The isolated compound had ultraviolet and infrared absorption spectra very similar to those of menaquinone. The mass spectrum of the compound showed the molecular ion peak at m/z 790 with the coexistence of two intense fragment ion peaks at m/z 225 and 187. However, two weak fragment ion peaks were not found at m/z 721(M-69) and 653 (M-69-68) due to the successive loss of isoprene units. The ¹H-NMR spectrum represented the signals of the following groups: 4×φ-H, δ 8.02-7.60; 6×-CH=C-, δ 5.04; Q-CH₂-, δ 3.32 (doublet, J=6.7Hz); Q-CH₃, δ 2.16; 10×=C-CH₂-, δ 1.98; =C-CH₃ (trans, 1st unit from quinone ring), δ 1.78; =C-CH₃ (cis, 9th unit), δ 1.66; 5×=C-CH₃ (trans, internal and 9th units), δ 1.57; 3×-CH₂-CH₂-CH-CH₂-, δ 1.28; 3×-C-CH₃, δ 0.90 (φ, benzene ring; Q, quinone ring). The chromenyl acetate was synthesized from the menaquinone, and was subjected to ozonolysis. The ozonolysis product had a mass spectrum showing ion peaks at m/z 464 (M⁺), 449 (M-15), 422 (M-42), 407 (M-15-42), 267, and 225. The results obtained indicated that the isolated menaquinone is formulated as 2-methyl-3-II, III, VIII-hexahydromultiprenyl⁹-1, 4-naphthoquinone.