Phytochemical and biological studies on Alnus glutinosa subsp. glutinosa, A. orientalis var. orientalis and A. orientalis var. pubescens leaves

Abstract

Ethnopharmacological relevance: Alnus species have been used for the treatment of rheumatism, hemorrhoids and for wound healing in folk medicine.

Materials and methods: Aqueous and methanol extracts of A. glutinosa (L.) Gaertner subsp. glutinosa, A. orientalis Decne. var. orientalis and A. orientalis var. pubescens Dippel leaves were evaluated for their wound healing, anti-inflammatory and antioxidant activities. In vivo wound models of linear incision and circular excision were performed. "Inhibition of acetic acid-induced capillary permeability", "carrageenan-induced hind paw edema" and T"PA-induced ear edema" assays were applied to determine the anti-inflammatory effects. For the antioxidant activity assessment, DPPH and ABTS radicals scavenging effect, reducing power and denaturation of nonspecific hydroxyl radical-targeted 2-deoxyribose were used. In vitro inhibitory effects on enzymes hyaluronidase, collagenase and elastase were evaluated. The methanol extract of the leaves of A. glutinosa subsp. glutinosa (MB), the most potent extract, was fractionated by bioassay-guided fractionation technique. The structure of the isolated compound was determined as shikimic acid by using NMR and IR analyses.

Results: MB increased the wound tension by 42.79% value and provided a contraction by 51.58%. Wound tension, contraction capacity and tissue hydroxyproline levels were increased with the application of the fraction EtOAc: MeOH (Fr. D), subfraction D_27-38 and shikimic acid. In the "inhibition of acetic acid-induced capillary permeability" assay, MB, Fr. D, subfraction D_27-38 and shikimic acid inhibited the permeability with significant inhibition values of 30.22%, 32.46%, 38.24% and 27.19%, respectively. In carrageenan-induced hind paw edema model, MB displayed 29.1% inhibition. Likewise, Fr. D, subfraction D_27-38, and shikimic acid were found to exhibit remarkable anti-inflammatory and antioxidant effects. Shikimic acid exhibited significant inhibitory effect (38.24%) on the hyaluronidase enzyme.

Conclusions: This is the first and unique study that investigates wound healing, anti-inflammatory and antioxidant effects of some Alnus taxons growing in Turkey. According to the results, shikimic acid was found to be the major compound responsible from the activity.

Keywords: Alnus; Anti-inflammatory; Antioxidant; Betulaceae; Isolation; Wound healing.