molecules Review The Botanical, Chemical and Ethnobotanical Diversity of Southern African Lamiaceae Ryan D. Rattray and Ben-Erik Van Wyk * Department of Botany and Plant Biotechnology, University of Johannesburg, Auckland Park, P.O. Box 524, Johannesburg 2006, South Africa; [email protected] * Correspondence: [email protected]; Tel.: +27-11-559-2412 Abstract: The Lamiaceae is undoubtedly an important plant family, having a rich history of use that spans the globe with many species being used in folk medicine and modern industries alike. Their ability to produce aromatic volatile oils has made them valuable sources of materials in the cosmetic, culinary, and pharmaceutical industries. A thorough account of the taxonomic diversity, chemistry and ethnobotany is lacking for southern African Lamiaceae, which feature some of the region’s most notable medicinal and edible plant species. We provide a comprehensive insight into the Lamiaceae flora of southern Africa, comprising 297 species in 42 genera, 105 of which are endemic to the subcontinent. We further explore the medicinal and traditional uses, where all genera with documented uses are covered for the region. A broad review of the chemistry of southern African Lamiaceae is presented, noting that only 101 species (34%) have been investigated chemically (either their volatile oils or phytochemical characterization of secondary metabolites), thus presenting many and varied opportunities for further studies. The main aim of our study was therefore to present an up-to-date account of the botany, chemistry and traditional uses of the family in southern Africa, and Citation: Rattray, R.D.; Van Wyk, to identify obvious knowledge gaps. B.-E. The Botanical, Chemical and Ethnobotanical Diversity of Southern Keywords: Lamiaceae; diversity; southern Africa; volatile oils; essential oils; phytochemistry; tradi- African Lamiaceae. Molecules 2021, 26, tional medicines; useful plants; medicinal plants; food plants 3712. https://doi.org/10.3390/ molecules26123712 ˙ Academic Editors: Ihsan Çalı¸s, 1. Introduction Horváth Györgyi and Agnieszka Ludwiczuk The Lamiaceae Martinov (formerly Labiate) are a commercially important, cosmopoli- tan family of flowering plants comprising ca. 250 genera and 7825 species [1]. The largest Received: 20 May 2021 and best-known genera include Salvia L. (900 spp.), Scutellaria L. (360 spp.), Stachys L. Accepted: 11 June 2021 (300 spp.), Plectranthus L’Hér. (300 spp.), Hyptis Jacq. (280 spp.), Teucrium L. (250 spp.), Vitex Published: 18 June 2021 L. (250 spp.), Thymus L. (220 spp.) and Nepeta L. (200 spp.). Many species are highly aro- matic and possess complex mixtures of bioactive secondary metabolites which contribute Publisher’s Note: MDPI stays neutral to their global importance as sources of medicinal and culinary herbs. Herbal teas that with regard to jurisdictional claims in are rich in aromatic and phenolic compounds, such as chamomile (Matricaria chamomilla published maps and institutional affil- L.), rooibos tea (Aspalathus linearis (Burm.f.) Dahlg.), maté (Ilex paraguariensis A.St.-Hil.) iations. and green tea (Camellia sinensis (L.) Kuntze) have become very popular [2,3] and it seems worthwhile to systematically explore the commercial potential of poorly known herbal teas. A recent global review of ca. 900 commercially important medicinal plant species [2] included 44 members of the Lamiaceae (ca. 5% of the total). Similarly, a review of major Copyright: © 2021 by the authors. food plants [3] listed 817 species, of which 43 (ca. 5%) belongs to the Lamiaceae. The Licensee MDPI, Basel, Switzerland. contribution of Lamiaceae species to the culinary herbs and spices of the world is even This article is an open access article more prominent with 114 species out of 701 listed (ca. 16%) [4]. The Lamiaceae also distributed under the terms and features prominently in a family-level analysis of medicinal plants used in Traditional conditions of the Creative Commons African medicine [5]. Due to their popular use, members of this family play a pivotal role Attribution (CC BY) license (https:// in many industries, including cosmetics, flavoring, fragrance, perfumery, pesticides and creativecommons.org/licenses/by/ pharmaceutical development. On account of their economic importance and wide-spread 4.0/). Molecules 2021, 26, 3712. https://doi.org/10.3390/molecules26123712 https://www.mdpi.com/journal/molecules MoleculesMolecules2021 2021, ,26 26, 3712, x FOR PEER REVIEW 2 ofof 5956 use,many many species species have have been beenintroduced introduced and cultivated and cultivated in various in various countries countries across across the world the world[6]. [6]. SouthernSouthern Africa Africa is is not not only only known known for for its its high high levels levels of plantof plant diversity diversity (20,401 (20, species)401 spe- andcies) plant and endemismplant endemism (67%) [(67]7 but%) [7] also but for also its culturalfor its cultural diversity, diversity, resulting resulting in a rich in ethnob- a rich otanicalethnobotanical heritage. heritage. Many important Many important aromatic, aromatic, medicinal medicinal and ornamental and ornamental plants plants have been have usedbeen forused centuries for centuries in traditional in traditional medicines medicines by indigenous by indigenous people people across across the the globe globe [8]. [8] A. bibliographyA bibliography of plants of plants used used in traditional in traditional medicine medicine in southern in southern Africa [ArnoldAfrica [Arnold et al. (2002)] et al. included(2002)] included 215 families, 215 families, equating equating to 3689 taxa to 3689 (comprising taxa (comprising species, subspecies species, subspecies and varieties) and andvarieties) represents and represents ca. 15% of theca. regional15% of the flora regional [9]. Some flora southern [9]. Some African southern representatives African repre- of thesentatives Lamiaceae of the are Lamiaceae well-documented are well as-documented traditional medicines,as traditional including medicines,Leonotis including leonurus Le- (L.)onotis R. Br.leonurus and Salvia (L.) R. africana Br. andL., Salvia as well africana as food L., andas well beverage as food plants and beverage (Coleus esculentus plants (Coleus(N.E. Br.)esculentus G. Taylor, (N.E.C. Br.) rotundifolius G. Taylor,(Poir.) C. rotundifo A. Chev.lius and (Poir.) Perrot A. and Chev.Mentha and aquaticaPerrot andL.) [10Mentha–14]. Inaquatica a review L.) of[10 150–14] important. In a review medicinal of 150 plants important of South medicinal Africa plants (Van Wyk of South et al. (2009)Africa [15(Van]), 15Wyk species et al. of (2009) Lamiaceae [15]), that15 species are commonly of Lamiaceae used inthat traditional are commonly medicine used were in traditional included (Figuremedicine1). were included (Figure 1). FigureFigure 1.1.Southern Southern AfricanAfrican medicinal medicinal plants plants of of the the Lamiaceae Lamiaceae that that are are commonly commonly used used in in traditional tradi- medicine:tional medicine: (A) Pseudodictamnus (A) Pseudodictamnus africanus africanus;(B) Mentha; (B) Mentha longifolia longifolia;(C) Leonotis; (C) Leonotis leonurus leonurus;(D) L.; ocymifolia(D) L. ; (Eocymifolia) Salvia; africana (E) Salvia;(F africana) S. aurea; (F;() GS. )aureaS. chamealaeagnea; (G) S. chamealaeagnea;(H) S. dentata; (H) S.;( dentataI) S. stenophylla; (I) S. stenophylla;(J) Stachys; (J) Stachys aethiopica; (K) S. linearis; (L) S. rugosa; (M) Tetradenia riparia; (N) Teucrium africanum and (O) aethiopica;(K) S. linearis;(L) S. rugosa;(M) Tetradenia riparia;(N) Teucrium africanum and (O) T. trifidum. T. trifidum. All photographs taken by B.-E. Van Wyk. All photographs taken by B.-E. Van Wyk. InIn thisthis detaileddetailed review,review, wewe provideprovide aa broadbroad overviewoverview ofof thethe botanicalbotanical diversity,diversity, re-re- portedported volatilevolatile andand otherother chemicalchemical compoundscompounds andand traditionaltraditional usesuses ofof thethe LamiaceaeLamiaceae inin southernsouthern Africa.Africa. The The geographical geographical area area covered covered isis the the Flora Flora of ofSouthern Southern Africa Africa region region (Figure 2), which includes South Africa, Botswana, Eswatini (Swaziland), Lesotho and Molecules 2021, 26, 3712 3 of 59 Molecules 2021, 26, x FOR PEER REVIEW 3 of 56 (Figure2 ), which includes South Africa, Botswana, Eswatini (Swaziland), Lesotho and Namibia. Our hypothesis was that the southern African Lamiaceae have remained poorly studied as a result of a lack of clarity on generic delimitations and phylogenetic relation- ships. The review therefore reflectsreflects on the current classificationclassification system of thethe familyfamily andand provides aa summarysummary ofof the the current current state state of of knowledge knowledge regarding regarding the the secondary secondary metabolites metabo- litesthat havethat have been been reported reported in the in literature,the literature, as well as well as traditional as traditional uses uses of southernof southern African Afri- canspecies species (data (data from from recent recent ethnobotanical ethnobotanical surveys surveys are included). are included). The aim The was aim to gainwas to a more gain profounda more profound understanding understanding of the patterns of the patterns of chemical of chemical variation variation and ethnobotanical and ethnobotanical diversity, diversity,and to identify and to obvious identify knowledge obvious knowledge gaps