molecules Article Quality Assessment of Commercial Spagyric Tinctures of Harpagophytum procumbens and Their Antioxidant Properties Pinarosa Avato * and Maria Pia Argentieri Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari Aldo Moro, via Orabona 4, 70125 Bari, Italy; mariapia.argentieri@uniba.it * Correspondence: pinarosa.avato@uniba.it; Tel.: +39-080-5442785 Received: 26 March 2019; Accepted: 14 June 2019; Published: 17 June 2019   Abstract: Preparations from the dried tubers of Harpagophytum procumbens (Burch.) DC ex Meisn, commonly known as devil’s claw, are mainly used in modern medicine to relieve joint pain and inflammation in patients suffering from rheumatic and arthritic disorders. This paper describes for the first time the chemical profile of a commercial spagyric tincture (named 019) prepared from the roots of the plant. For comparison purposes, a commercial not-spagyric devil’s claw tincture (NST) was also analyzed. Chemical investigation of the content of specialized metabolites in the three samples indicated that harpagoside was the main compound, followed by the two isomers acteoside and isoacteoside. Compositional consistence over time was obtained by the chemical fingerprinting of another spagyric tincture (named 014) from the same producer that was already expired according to the recommendation on the label of the product. The two spagyric preparations did not show significant compositional differences as revealed by HPLC and MS analyses, except for a decrease in harpagide content in the expired 014 tincture. Moreover, their antioxidant capacities as assessed by 2,2’-di-phenyl-1-picrylhydrazyl (DPPH) and 2.2’-azin-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods resulted in very similar IC50 values. The expired 014 tincture showed instead a lower IC50 value compared to the 019 and NST tinctures with the ferric reducing antioxidant potential (FRAP) assay, indicating a higher ferric-reducing antioxidant ability. Overall, these results indicated that the two preparations could generally maintain good stability and biological activity at least for the four years from the production to the expiration date. Keywords: Harpagophytum procumbens; devil’s claw; harpagoside; spagyric tincture; antioxidant activity 1. Introduction Harpagophytum procumbens (Burch.) DC ex Meisn, commonly known as devil’s claw, is a plant native to southern Africa, where it is traditionally used as a bitter tonic and a stomachic and also for the treatment of fever, gout, myalgia, and arthritis [1,2]. Accordingly, preparations from the dried tubers of the plant are mainly used in modern medicine and as health products to relieve joint pain and inflammation in patients suffering from rheumatic and arthritic disorders. Clinical studies have in fact shown that extracts from the roots of this plant are good therapeutic remedies for degenerative diseases of the musculoskeletal and locomotor systems [1,3]. In addition, the use of devil’s claw secondary tubers is also approved in preparations for the relief of mild digestive disorders and for the temporary loss of appetite [4,5]. The European Medicines Agency (EMA) recommends preparations obtained by comminuting or powdering the roots of the plant. Liquid, soft, or dry extracts for oral use made in ethanol or water Molecules 2019, 24, 2251; doi:10.3390/molecules24122251 www.mdpi.com/journal/molecules