Research on plant extracts and phytochemicals: criteria for evaluation

Abstract

et al. 2013; Ke˛dzierska et2013; Abdel-Salam etal. al. 2012; Cakmak et al. 2012; Naghiloo et al. 2012 ), antimi-crobial (Prachayasittikul et al. 2008; Salleh et al. 2012; Zhu et al. 2011; Darabpour et al. 2011), apoptotic and antiapop-totic (Mishra and Kumar 2009; Ogata et al. 2010; Lu et al. 2009), hypolipidemic (Ansarullah et al. 2009 ; Amran et al. 2012; Ikewuchi 2012a), antidiabetic (Zardooz et2012al., ; Ikewuchi 2012b), antitumor (Guo and Wang 2009; Khalil et al. 2008; Zeeshan et2012 al. ; Tian et2012al. ; Park 2012), anticonvulsant (Bhat et2012a, al. b), antiarrhyth-mic (Jahanbakhsh et2012 ; Esmailidehaj etal. 2012 al. ) and anti-inflammatory (Motavallian-Naeini et2012; al. Kamarudin et al. 2012; Su et al. 2011) substances.We, at the Archives of Toxicology, receive numerous contributions from scientists whose research focus on the effects of natural compounds. Unfortunately, a relatively high fraction of these manuscripts is rejected by our board of reviewers. This prompted the editors, in the current Edi-torial, to communicate their criteria for evaluation—which are of course open for comments and discussion. Many of the several hundred studies which were turned down for publication have all used a similar approach. They usually begin by describing how various plant extracts are acquired, without any further characterization of the extracts them-selves. Nevertheless, these extracts are added to cells with and without a toxic compound, in an attempt to demon-strate some protective effect. Such studies are usually rejected, because the compounds in the extracts responsible for the protective effect remain unidentified. Therefore, to increase the chance of acceptance, we propose that the sub-mitted studies fulfil the following criteria:• Bioactive compounds from plant extracts that have been isolated should be identified and their efficiency demon-strated.In the 1990s, the pharmaceutical industry introduced robots that could synthesize thousands of different small mol-ecules in a very short time. Soon, compound libraries with millions of combinatorially produced substances became available. However, despite these impressive numbers, the results were disappointing. Almost all of the produced substances were biologically irrelevant. In addition, the boom in substance research yielded no progress in drug development.This failure led to a shift in strategy. Many groups sub-sequently chose to design their compound libraries based on small biologically active molecules found naturally in plants, animals and microorganisms. The obvious advan-tage of this strategy was the millions of years of evolution that went into optimizing how these natural compounds interact with cells and organisms, for example as messen-gers or for defence. It is not surprising that many of the cur -rently used drugs, such as taxanes, digitalis, morphine or salicylic acid, have been derived from nature.Currently, enormous efforts are placed on analysing plant extracts for possible medical applications (Geb-hardt 2000; Smith et al. 2013; Katalinic et al. 2006; Wag-ner 2011; Radojevic et al. 2012; Vasic et al. 2012; Onocha et al. 2011). Examples are hepatotropic (Kheir Eldin et al. 2008; Young et al. 2007; Jain et al. 2012; Eidi et al. 2012; Ikewuchi et2011a al. , b; Godoy 2011), neurotropic (Qu et al. 2012; van Thriel 2011) and nephrotropic (Venkatan-arayana etal. 2012) compounds, as well as antioxidative (Prachayasittikul et2009 al. ; Lee et al. 2007; Takashima