Morinda citrifolia Inhibits Both Cytosolic Ca<SUP>2＋</SUP>-dependent Phospholipase A<SUB>2</SUB> and Secretory Ca<SUP>2＋</SUP>-dependent Phospholipase A<SUB>2</SUB>

Morinda citrifolia Inhibits Both Cytosolic Ca<SUP>2＋</SUP>-dependent Phospholipase A<SUB>2</SUB> and Secretory Ca<SUP>2＋</SUP>-dependent Phospholipase A<SUB>2</SUB>

This study investigated the effects of the methanol extracts of Morinda citrifolia containing numerous anthraquinone and iridoid on phospholipase A₂ (PLA₂) isozyme. PLA₂ activity was measured using various PLA₂ substrates, including 10-pyrene phosphatidylcholine, 1-palmitoyl-2-[¹⁴C]arachidonyl phosphatidylcholine ([¹⁴C]AA-PC), and [³H]arachidonic acid (AA). The methanol extracts suppressed melittin-induced [₃H]AA release in a concentration-dependent manner in RAW 264.7 cells, and inhibited cPLA₂/sPLA₂-induced hydrolysis of [¹⁴C]AA-PC in a concentration- and time-dependent manner. A Dixon plot showed that the inhibition by methanol extracts on cPLA₂ and sPLA₂ appeared to be competitive with inhibition constants (K_i) of 3.7&#1356;g/ml and 12.6&#1356;g/ml, respectively. These data suggest that methanol extracts of Morinda citrifolia inhibits both Ca^2＋-dependent PLA₂ such as, cPLA₂ and sPLA₂. Therefore, Morinda citrifolia may possess anti-inflammatory activity secondary to Ca^2＋- dependent PLA₂ inhibition.