Methoxylated Flavones from Salvia Mirzayanii Rech. f. and Esfand with Immunosuppressive Properties

Aerial parts of Salvia Mirzayanii was extracted with methanol. Methanol extract was suspended in water and defatted with petroleum ether. The defatted part was then partitioned between ethyl acetate and water. The ethyl acetate partition was chromatographed on a silica gel column to afford several fractions. Lymphocyte proliferation inhibitory assay of the resulted fractions was compared in vitro and the fraction with more immunosuppressive activity was subjected to more purification to yield three methoxylated flavones: 5,7-dihydroxy,6,4'–dimethoxyflavone(1), 5-hydroxy,6,7,3',4'–tetramethoxyflavone(2) and 5,3'-dihydroxy,6,7,4'–trimethoxyflavone (3). Compounds 2 and 3 potently suppressed the proliferation of human blood lymphocytes with IC50 values of 1.3 ± 0.04 μg/mL and 1.3 ± 0.21 μg/mL in comparison with prednisolone as one of the lymphocyte suppressor drugs (IC50=1.45 ± 0.6 μg/mL). In phagocyte chemiluminescence assay, compounds 1 and 3 in peripheral mononuclear cells (PMNCs) exerted suppressive moderate activity against ROS with IC50 of 55.3 ± 0.4 and 36.2 ± 0.7 μg/mL, respectively, while compound 2 showed weak activity with IC50 values more than 100 μg/mL. In conclusion, compounds 2 and 3 have a similar suppressive effect more than compound 1 on PHA-activated lymphocyte proliferation, which might be because of their C-3' oxidation pattern of ring B. It is indicated that the presence of 3'-OH or 3'-OMe in flavone ring B, caused more anti-proliferation activity than 3'-H. Oxidative burst assay showed more activity for compound 1 which is less methoxylated than others. It also showed more activity for compounds 3 than 2, which differ only in 3'-OH instead of 3'-OMe.