Biological activity of some naturally occurring resins, gums and pigments against in vitro LDL oxidation

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Abstract
Naturally occurring gums and resins with beneficial pharmaceutical and nutraceutical properties were tested for their possible protective effect against copper‐induced LDL oxidation in vitro. Chios mastic gum (CMG) (Pistacia lentiscus var. Chia resin) was the most effective in protecting human LDL from oxidation. The minimum and maximum doses for the saturation phenomena of inhibition of LDL oxidation were 2.5 mg and 50 mg CMG (75.3% and 99.9%, respectively). The methanol/water extract of CMG was the most effective compared with other solvent combinations. CMG when fractionated in order to determine a structure–activity relationship showed that the total mastic essential oil, collofonium‐like residue and acidic fractions of CMG exhibited a high protective activity ranging from 65.0% to 77.8%. The other natural gums and resins (CMG resin ‘liquid collection’, P. terebinthus var. Chia resin, dammar resin, acacia gum, tragacanth gum, storax gum) also tested as above, showed 27.0%–78.8% of the maximum LDL protection. The other naturally occurring substances, i.e. triterpenes (amyrin, oleanolic acid, ursolic acid, lupeol, 18‐a‐glycyrrhetinic acid) and hydroxynaphthoquinones (naphthazarin, shikonin and alkannin) showed 53.5%–78.8% and 27.0%–64.1% LDL protective activity, respectively. The combination effects (68.7%–76.2% LDL protection) of ursolic‐, oleanolic‐ and ursodeoxycholic‐ acids were almost equal to the effect (75.3%) of the CMG extract in comparable doses. Copyright © 2003 John Wiley & Sons, Ltd.