• First published: 27 May 2016

Joanna Kolodziejczyk-Czepas

Abstract

Objectives

Clovers (Trifolium, Fabaceae) have a long history of use in folk medicine. Furthermore, during last 3 years, a considerable growth in scientific interest in these plants has been observed. This article summarizes and critically reviews an over 3-year progress of knowledge of ethnomedicinal use, phytochemical profile, physiological effects and possible therapeutic action of various clover species. It contains the latest literature (over 80 papers), originated from international databases (MEDLINE/PubMed, Science Direct/Elsevier, Springer Link, Wiley Online Library) and reports from other international and local scientific periodicals.

Key findings

Traditional uses of T. pratense and T. repens have been confirmed, while the folk medicine recommendations for administration of other clovers such as T. burchellianum, T. fragiferum, T. hybridum, T. minus and T. purpureum were reported for the first time. Furthermore, several other clover species were also investigated in terms of their antioxidant, antimicrobial and phytoestrogenic effects for the first time. Only T. alexandrinum, T. pratense and T. medium were examined in animal studies.

Summary

Besides T. pratense, other clovers may be a rich source of bioactive phytochemicals. However, in contradiction to red clover, the therapeutic use of other clovers is still limited by the lack of in-vivo evidence.

Introduction

Despite ethnomedicinal uses and agricultural value of clovers (Trifolium, Fabaceae), the chemical composition and pharmacological properties of clover-derived preparations for a long time were out of scientific interest in the field of medicinal plants and search for natural sources of bioactive compounds. Before publishing the previous review (covering articles available until July 2012),1 very few clover species had been investigated in terms of their phytochemical profile and possible therapeutic uses. Most of reports concerned red clover (T. pratense L.), the best known member of Trifolium genus, while other clover species were treated marginally. The recent years have provided a noticeable increase of interest in clovers as a valuable source of bioactive compounds or a base for nutraceuticals, dietary supplements and herbal medications. Both red clover and other clover species have been more extensively investigated in vitro and in vivo. When compared to all data collected in the previous review,1 the number of publications related to chemical composition and biological properties of different clovers has grown more than double.

This study summarizes and critically reviews an over 3-year progress in studies on clovers, including the latest information on chemical profile, biological activity and possible medicinal importance of recent findings concerning different Trifolium plants and current limitations of their use as herbal drugs or supplements. It presents the newest evidence and novel trends in research on Trifolium plants, comprehensive chemical analyses as well as findings from different types of studies on both well-known and less described clover species.

The review comprises scientific (peer-reviewed) data published between July 2012 and March 2016, derived from ethnomedicinal surveys, in vitro, in vivo and in silico examinations as well as meta-analyses, available in international databases (MEDLINE/PubMed, Science Direct/Elsevier, Springer Link, Wiley Online Library). Reports from other international as well as local scientific journals that are not indexed in these databases but are available online in Google Scholar or repositories and libraries of different academic institutions have been also included. The search criteria contained the following keywords: ‘Trifolium’ or ‘clover’ and their combinations with other words, that is medicine, ethnomedicine, phytomedicine, traditional medicine, therapy, phytotherapy, herbal therapy, dietary supplements, ethnobotany, pharmacy, pharmacognosy, chemical profile, phytochemistry, bioactive compounds (including the names of different groups of phenolic substances), estrogen and phytoestrogens. Unpublished works/results and commercial materials were excluded from this study.

Clovers in traditional medicine

In folk medicine of different world regions, clovers have been known for centuries.1–8 For 3 years, over 20 new scientific reports confirming ethnomedicinal value of different Trifolium species have been appeared (both earlier findings and the newest data are summarized in Table 1). Red clover, the most recognized of the Trifolium species, has been widely described in regard of both agricultural relevance and pharmacological action (estrogenic effects, in particular). A broad range of ethnomedicinal recommendations for use of this plant has been recently extended by reports confirming its traditional use in the treatment of bronchitis, burns, sedation,9 polycystic ovarian syndrome10 and heart disorders11 or as antidiabetic drug12 and laxative.13 Besides the therapeutic use, flowers of red clover are listed as one of the wild plant foods traditionally consumed in Bologna (Italy)14; eating nectar from the flowers in Slovakia15 has been also reported. Furthermore, T. pratense belongs to wild food plants consumed in Elazığ (Turkey),16 while aerial parts of T. repens are wild plant food in northwest Yunnan Province (China).17 Additionally, the use of edible flower extracts of T. pratense and T. repens as promising functional ingredients of human diet is suggested.18

Reference:

https://onlinelibrary.wiley.com/doi/full/10.1111/jphp.12568