Alnuheptanoid B: A New Cyclic Diarylheptanoid from Alnus japonica Stem Bark

A new cyclic diarylheptanoid namely alnuheptanoid B (3), along with four known cyclic diarylheptanoids: myricanone (1), (+)-S-myricanol (2), myricanone 5-O- b -D-glucopyranoside (4), and (+)-S-myricanol 5-O- b -D-glucopyranoside (5) were isolated from Alnus japonica Steud (Betulaceae) stem bark. Their structures were determined by spectroscopic analyses, including UV, IR, 1D ( 1H and 13C), 2D (COSY, HMQC, and HMBC), and HRESIMS, as well as optical rotation measurement. Compounds 1, 2, 4, and 5 are reported for the first time from the plant. All isolated compounds 1-5 were tested for their antioxidant and anti-inflammatory activities using DPPH assay and carrageenin induced rat paw edema model, respectively. They displayed significant antioxidant activity in relation to propyl gallate (positive control). Compound 2 demonstrated anti-inflammatory effect at a dose 10 mg/kg.