POLYPHLORETIN PHOSPHATE (PPP) ANTAGONISTS OF PROSTAGLANDIN ACTION ALSO INHIBIT PROSTAGLANDIN BIOSYNTHESIS INVITRO

Abstract— Several polyphloretin phosphate (PPP) fractions (low mol. wt LC1259; high mol. wt LC1261; crude mixture, LC101) were confirmed in their established property as antagonists of the pharmacological actions of prostaglandins in a preparation of guinea‐pig isolated ileum stimulated by prostaglandin (PG)E2. Further samples of the same material were then compared in‐vitro with indomethacin in their ability to inhibit prostaglandin biosynthesis from arachidonic acid by a microsomal enzyme preparation. All three PPP fractions potently inhibited prostaglandin generation, with the rank order of potency LC1259 = LC101 = indomethacin > LC1261. The oral LD50 in mice was 25 mg kg−1 for indomethacin and > 1 g kg−1 for LC101. PPP fractions (especially LC101) may therefore have therapeutic potential as anti‐inflammatory agents. 1990 Royal Pharmaceutical Society of Great Britain