Indonesian medicinal plants. XXIII. Chemical structures of two new migrated pimarane-type diterpenes, neoorthosiphols A and B, and suppressive effects on rat thoracic aorta of chemical constituents isolated from the leaves of Orthosiphon aristatus (Lamiaceae).

Two novel migrated pimarane-type diterpenes named neoorthosiphols A (1) and B (2) were isolated from the water decoction of the leaves of Orthosiphon aristatus (Lamiaceae), which has been prescribed in Javanese traditional medicine (jamu) for the treatment of hypertension, etc. The absolute chemical structures have been elucidated on the basis of physicochemical properties. It has been found that two migrated pimarane-type diterpenes (1, 2), four isopimarane-type diterpenes (3, 4, 5, 6), three benzochromenes (7, 8, 9) and two flavones (12, 13) exhibit a suppressive effect on contractile responses in rat thoracic aorta, among thirteen chemical constituents (1-13) isolated from the leaves.