Ethnomedicinal uses, biological activities, phytochemistry and conservation of African ginger (Siphonochilus aethiopicus): a commercially important and endangered medicinal plant

Ethnopharmacological relevance: In sub-Saharan Africa, African ginger (Siphonochilus aethiopicus) is used for treating common illnesses including colds, coughs, inflammation and related symptoms. The available literature survey on this plant provided scarce anecdotal information, particularly in western and eastern Africa, with a few reports on bioactivity. In addition, the indigenous knowledge and conservation strategies of this economically important and critically endangered species are currently fragmented.

Aim of the review: This review entails a critical appraisal of existing literature on the ethnomedicinal uses, biological activities, phytochemicals, research opportunities and prospects for the sustainable use of S. aethiopicus.

Materials and methods: This review was conducted using a comprehensive literature search on the ethnomedicinal uses, biological activities and phytochemistry of S. aethiopicus throughout its distributional range. The conservation status and associated bio-economy potential of African ginger were also assessed. We searched different online databases (e.g. Google Scholar, ScienceDirect, PubMed and Scopus) for peer-reviewed journals, conference outputs, international, regional and national organizational reports, published books and theses.

Results: We established that S. aethiopicus is used to treat a wide variety of ailments such as respiratory problems (including cough, influenza), pain, inflammation and malaria. Extracts of African ginger are used as an ingredient in some commercialised products for nutraceutical, cosmeceutical and pharmaceutical purposes. The rhizome extract demonstrated anti-asthmatic, anti-inflammatory, and antiplasmodial activities, which led to the development of a patented novel extract for treating asthma and allergies. Phytochemical analysis of leaf, root and rhizome extracts of African ginger revealed the presence of flavonoids, phenolic acids, volatile and essential oils as major constituents. These phytochemicals are known to possess bioactivities such as antimicrobial and anti-inflammatory activities. Particularly, the bioactive compounds, siphonochilone and eucalyptol, found in the roots and rhizomes have demonstrated potential to be used in remedies for treating asthma and allergic reactions. Furthermore, extracts of S. aethiopicus contained natural anti-inflammatory mediators with potentials to combat and manage chronic inflammation. This plant is classified on the Red List of South African Plants as a critically endangered plant. Its high risk of extinction due to its unsustainable harvesting and exploitation necessitate its rapid propagation and cultivation to meet its increasing demand.

Conclusions: The review highlights the therapeutic potential of S. aethiopicus and rational prioritization of this plant species with the potential for isolating new bioactive compounds. In the light of the use of this plant extract in traditional medicine and many commercial products, there is a heightened need to explore the mechanism(s) of action of the identified extracts and bioactive compounds in order to fully understand their pharmacokinetics and probably elucidate the pathways of their activities.

Keywords: Allergies; Zingiberaceae; anti-inflammatory; asthma; conservation; eucalyptol; siphonochilone; wild ginger.