A Metalloproteinase Inhibitor from Doliocarpus verruculosus

Abstract

In our natural products screening programme for the discovery of competitive inhibitors of the matrix metalloproteinases, stromelysin and collagenase, we have isolated an active compound, betulinic acid (l), from the plant Doliocarpus uerruculosus. Betulinic acid inhibits stromelysin and collagenase with Ki values of 2.2 and 1.3 CM, respectively. The analogous C-28 alcohol, betulin, was a less potent inhibitor of these proteases. We therefore postulate that the moiety of 1-carboxyl-3-(2-propenyl)-cyclopentane in betulinic acid may mimic the hydroxamate-containing residue of actinonin (3), a known stromelysin and collagenase inhibitor. Because a hydroxamate can serve as a bidentate ligand for the active site zinc, we synthesized the hydroxamate of 3acetoxy-betulinic acid (2), hoping to observe an increase in potency relative to 1. However, the Ki values against stromelysin and collagenase were essentially equal to those of 1. These data suggest that the rigid cyclopentyl ring is probably restricting the tight binding as seen in the flexible peptidal hydroxamates, or the acid moiety is not interacting directly with the active site zinc of the metalloproteinases.

Design and Therapeutic Application of Matrix Metalloproteinase Inhibitors

“…Few of the other leads identified from natural products have been as amenable to optimization. Among the more interesting are nicotianamine, betulinic acid, glycyrrhetinic acid, and rifampicin . All of these compounds exhibit weak inhibitory activity, and in the absence of any information about their interaction with the enzymes active site, it is unclear how to best optimize their activities.…”

Intricate Functions of Matrix Metalloproteinases in Physiological and Pathological Conditions

“…Hydroxamic acids as well as piperazic acid derivatives have also shown to exert MMP inhibition activity against MMP‐3 by establishing hydrogen bonds between the carbonyl and amide NH of Tyr‐233 and the enzyme's carbonyl oxygen at Asp‐162 (Tamaki et al, ). Furthermore, nicotinamine (Suzuki et al, ), betulinic acid (Sun et al, ), glycyrrhetinic acid (Bae et al, ), and rifampicin (Di Giulio et al, ) all show weak inhibitory activity via unknown mechanisms.…”

A study of the anti-invasive properties of N-α-phthalimidomethyl-ketomethylene tripeptide-based metalloprotease inhibitors

“…While some recent reports have described the use of pharmacologically active natural products, such as tetracyclines (Bols et al 1992), betulinic acid (Sun et al 1996) and nicotianamine (Suzuki et al 1996) as moderately effective MMP inhibitors, the principal drug design strategy still remains the development of compounds incorporating a metal-chelating moiety into a synthetic substrate or non-substrate-based targeting group. Such chelating groups bind to the zinc atom present in the active site of all MMPs thereby preventing substrate hydrolysis.…”