Traditional Uses, Phytochemistry, and Pharmacology of Elegia Species: A Review

: In South Africa, plants belonging to the Restionaceae family possess an ecological dominance. As a result, they have been the subject of numerous morphological, anatomical, and evolutionary studies. However, few studies have focused on their phytochemical proﬁle and their potential pharmacological activities. The genus Elegia L. is the second largest of this family comprising 52 species, which are mainly used as materials for thatching. Limited studies on the chemical constituents of Elegia species and their importance as medicinal plants have been undertaken. This review provides constructive and extensive information about the botanical characterization, distribution, traditional uses, phytochemistry and pharmacology of the genus Elegia . A comprehensive search of previously published literature was performed for studies on this genus, using databases with different key search words. This survey documented 52 Elegia species summarizing their previous taxonomic classiﬁcation. In addition, 14 species were found to be studied for their phytochemical proﬁle, revealing 14 chemical compounds. Concerning their biological activities, only one species ( E. tectorum (L.f.) Moline and H.P.Linder) is reported for its anti-wrinkle activity. Moreover, two species are locally used for thatching and as materials for brooms. The present review highlights the Elegia genus as an important source of bioactive phytochemicals with ﬂavonol glycosides being the main metabolites and reveals the uncharted territory of this genus for new research studies.


Introduction
Restionaceae is an ancient family, related to grasses and sedges, which includes 60 genera and over 500 species [1][2][3].It is distributed throughout the southern hemisphere with the majority of its populations occurring in Africa (approximately 360 species) and in Australia (approximately 150 species) [1,3].Plants of this family are known as restios and possess a dominant ecological role in the Cape Floristic Region of South Africa.Fynbos is the main vegetation of this biodiversity hotspot and restios are considered its characteristic component [1,4].
In general, the taxonomy of this family is challenging and is constantly modified due to new genetic data [5].The African species belong to Restionoidae Mast.subfamily, which consists of approximately 16 genera and 360 species.The Restionoidae subfamily is further divided into 2 tribes, Restioneae Bartl.and Willdenowieae Masters [1,6].The Willdenowieae tribe contains 8 genera, while the rest belong to the Restioneae tribe.Within the Restioneae tribe, there are several groups, one of which is the Elegia group including two genera, Elegia L. and Askidiosperma Steud.[1].The name Elegia has Greek origin and derives from the ancient Greek word "elegeia" which means ode and the root word "elegos" Sci.Pharm.2022, 90, 4 2 of 11 which translates as lament, mourning or mourning song accompanied by a flute.The word was later used by Plinius in the Latinized form to describe a kind of reed [5].
The Restionaceae family shows an intriguing ecological dominance in South Africa [1].Consequently, plants of this well-known family have been the subject of numerous morphological, anatomical and evolutionary studies [4,6].However, the absence of reports on potential pharmacological activities and the lack of up-to-date scientific studies of the phytochemistry are enthralling facts that led us to thoroughly study the restios and especially the genus Elegia.Recently, E. tectorum revealed promising anti-wrinkle activity.Thus, the aim of this review was to provide constructive and extensive information about the botanic characterization, distribution, traditional uses, phytochemistry and pharmacology of the genus Elegia with the hope of further exploration of the scientific potential of these plants.

Materials and Methods
A comprehensive literature search was conducted on scientific databases including Google Scholar, PubMed and Reaxys.The keywords "Elegia", "Restionaceae", "Restios", "Elegia compounds", "Elegia phytochemicals", "Elegia pharmacological" and "Elegia traditional uses" were used for data collection.The number of searches/hits for each keyword is presented in Table 1.The criteria for the selection of the used articles were studies on the traditional uses, phytochemistry and pharmacological properties of this genus.Searches were performed for other potential studies by manual screening references in the used research articles.Moreover, books with rigorous quality of taxonomic information and ethnobotany were selected for the review.The latest date for searching the literature was 15 October 2021.The time range of data collection was from 1969 to 2021.The taxonomy of the African Restionaceae available in IntKey format as a free download from the website of the University of Zurich was used to validate the scientific names, provide information about the distribution, botanical characterization and traditional uses of the African species [7].The Elegia species with their botanical synonyms (previous botanical names) are displayed in Table 2, the specialized natural products reported in the genus Elegia are categorized by species in Table 3 and the chemical structures of the identified compounds are illustrated in Table 4.

Botanical Characterization and Distribution
The plants of the Restionaceae family are found all over the southern hemisphere with approximately 360 species in Africa, 150 in Australia, 4 in New Zealand, 1 in Southwest Asia and 1 in South America.All the species of the genus Elegia are endemic to the Western and Eastern Cape Province of South Africa [1,3].The genus Elegia L. is the second largest of the family with 52 species (Table 2) [5,7].
Plants of the Restionaceae family are evergreen, grass-like plants, caespitose, rhizomatous or stoloniferous, growing to a maximum height of 3.5 m (depending on the species) [1,3].Species belonging to the Elegia L. are either caespitose or rhizomatous [3].The stems of the restios are called culms and they are the only green part of the plant and are, therefore, considered as the main photosynthetic organ [1,3].The culms of the Elegia species could be simple or branched.The leaves of the restios are reduced to sheaths in adult plants, they can also be persistent, but usually the plants lose these sheaths.Male and female inflorescences are usually similar, much branched with numerous small, often dark-coloured spikelets or solitary flowers [1,3].Spikelets consist of flowers and large bracts (a modified leaf) that are called spathes.Spathes are prominent and often obscure the flowers [1].Restios' flowers have three petals and three sepals forming a perianth of six tepals whose color, shape, size and texture vary for each species [1].Each flower is minute (<10 mm long) and is situated on a central axis above a bract.The fruit can be either a 1-3 locular capsule or a 1-locular nut [1,3].The seeds have an elliptical shape and are between 1-2 mm long [1].
The entire family is wind-pollinated and all genera apart from Coleocarya S.T. Blake and Lepyrodia R. Br. are dioecious.The enlarged bracts and spathes of the Elegia genus appear to work as air scoops, that guide the wind to pass through the styles.Alternatively, they are able to cause local eddies that help the pollen drop down onto the styles.These mechanisms have a high efficacy, since very little pollen of other species has been detected on the styles of the Elegia species [1].

Traditional Uses
The traditional use of herbs is an integral part of the culture and religious practices/rituals of African people.It is estimated that over 80% of the South African population has consulted local therapists who employ traditional methods and treatments, using various parts of native plants at least once in their lives [8].To date, numerous cultural communities of the region depend on traditional medicine, called "muthi", instead of the modern western medicine [9].South Africa has a multitude of tribes, each of which uses its own remedies [8,10].It is estimated that more than 3400 medicinal species exist in southern Africa of which 2062 taxa have been identified as being used and/or sold in this region [9].These taxa belong to 171 families with the 5 most popular medicinal plant families being the Asteraceae (2236 species; 257 medicinal species), Fabaceae (1638 species; 159 medicinal species), Apocynaceae (689 species; 104 medicinal species), Asphodelaceae (558 species; 83 medicinal species) and Lamiaceae (264 species; 68 medicinal species) [9].Despite the large contribution of restios to the local flora (over 360 spp. in Africa), Williams et al. (2013) reported that only one species is documented as a medicinal plant, but its common or botanical name was not mentioned [9].However, some species of the family have been recorded in ethnobotany, still they are all only used as materials for the manufacture of tools such as brushes and dusters [10].Among them, two Elegia species (E.equisetacea and E. tectorum) are used for thatching and as materials for brooms [1,10].
Plants of Restionaceae family are widely used by the local populations with their main purpose being as a building material for roof thatching [1,3].Several of them were used as building materials in many areas of South Africa long before the first European colonies arrived.These constructions can still be seen in locations where traditional "reed" houses continue to be built and maintained in a similar way.The culms in particular are used for the construction of various parts of the houses such as roofs and walls [1].During the Dutch East India Company's presence in the Western Cape, E. tectorum (L.f.) Moline and H.P. Linder was one of the most used species for thatching [1,5].Due to its strong presence in the flora of the surrounding area, it is was probably the main plant employed to build the roofs of what is now modern Cape Town several centuries ago [7].Nowadays, thatching is prepared mostly from Thamnochortus insignis Mast.Apart from thatching, some species are locally used as materials for brooms.In current years, there is an increasing use of restios for ornamental purposes since they are ideal for areas with water shortages [1].

Phytochemistry
Although the Restionaceae family has been in existence for over 200 years, few phytochemical studies of this family have previously been conducted.Studies, which have investigated the phytochemical composition of species in this family, have highlighted the flavonoid compounds.The flavonoid patterns of the Restionaceae family present differences compared to those of the related families, Juncaceae and Poaceae.In addition, various flavonoids derivatives were reported among the taxa of the restios, which could be attributed to the geographical origin [3,11,12].In particular, the African species are rich in common 3-hydroxyflavones (flavonols) and flavones as aglycons or/and with their glycosides.In the genera Elegia and Chondropetalum, the presence of glycosides of myricetin, laricitrin and syringetin and the absence of glycosides of flavones distinguishes them from the rest of the African taxa [3,11].The rest of the African genera contain glycosides of quercetin and glycosides of various flavones.Specifically, the flavones are luteolin, apigenin, chrysoeriol, cyanidin, orientin, iso-orientin and lucenin [11].In contrast, the Australian species are characterized by the existence of the flavonol, gossypetin, and the absence of proanthocyanidins which can be found in almost all of the African species [3,11].Interestingly, from the 42 African species that were examined, 88% of them contained proanthocyanidins, while only 4% of the 115 Australian species contained them [13].Moreover, the presence of gossypetin instead of quercetagetin is considered as a characteristic of a more "ancient" family since the latter is found in families that are more chemically advanced.This hypothesis is supported by the phylogenetic theory that Restionaceae is a relatively unspecialized family and is ancestral to the Poaceae and the Eriocaulaceae [14].
A study by Harborne et al. (1985) investigated 11 species of the genus Chondropetalum, showing that even within the genus there are differences in the chemical profile of the flavonoids.In contrast, many of these species revealed numerous similarities with species of the genus Elegia.In fact, most of the examined Chondropetalum species were eventually reclassified and now belong to the genus Elegia and the rest are classified in the genus Askidiosperma [2,7].According to Harborne et al. (1985) the species were divided into two groups based on their 3-hydroxyflavone (flavonol) aglycons.The first group included most species re-classified to the genus Elegia and contained glycosides of myricetin, laricitrin and syringetin.Whereas the second group consisted of mainly Askidiosperma species, which contain quercetin, kaempferol, gossypetin, 7 -methyl-ether of gossypetin and herbacetin 4 -methyl ether.It is important to note that the different flavonoid quantity of E. macrocarpa resulted in the classification of this species into the second group.With regards to the presence of proanthocyanidins, both procyanidin and prodelphinidin were identified in species of the first group (Elegia species), while only procyanidin was present in the second group [12].The chemical structures of the reported natural products from the genus Elegia are presented in Tables 3 and 4.
Proanthocyanidins have been mentioned to possess various and promising pharmacological properties [29].In particular, they have shown antioxidant, anticancer, antidiabetic, neuroprotective, and antimicrobial activities.Thus, their presence reinforces the already pharmaceutically interesting phytochemical profile of Elegia species.
The species E. tectorum was included in a recently conducted research project that investigated the potential of twenty-seven indigenous South African plants.They were tested for the treatment of acne, skin hyperpigmentation, wrinkles (elastase inhibition), periodontal diseases, tuberculosis and cancer [30].The ethanolic extract of E. tectorum was studied for its antibacterial activity against Cutibacterium acnes, Prevotella intermedia, Streptococcus mutans, Mycobacterium tuberculosis and M. smegmatis.The method used was the serial microtiter dilution assay in which the minimum inhibitory concentration (MIC) values for plant extract were measured.Furthermore, the ethanolic extract was explored for inhibition activity against elastase and tyrosinase, which are enzymes associated with wrinkle formation and pigmentation, respectively.Moreover, the cytotoxicity were tested against human keratinocytes (HaCat), melanoma cells (MEL-1), breast cancer cells (MCF-7) and cervical cancer cells (HeLa) [30].The results showed that E. tectorum exhibited no antibacterial or cytotoxic activity.However, it displayed a moderate anti-tyrosinase activity with an IC 50 value of 65.26 ± 8.38 µg/mL and potent anti-elastase activity with an IC 50 value of 13.5 ± 1.5 µg/mL.The inhibitory activity against elastase of E. tectorum was comparable to ursolic acid, a known inhibitor of elastase.It is worth noting that after consecutive liquid/liquid partitions with ethyl acetate and saturated butanol three fractions were obtained.Of these fractions, the remaining aqueous fraction had the highest anti-elastase activity, but its IC 50 value was lower compared to the initial ethanol extract.Furthermore, the aqueous fraction was submitted to further chromatographic techniques and gave six subfractions, of which none anti-elastase activity.Thus, the author assumed that this activity was possibly correlated to synergistic effects with the compounds presented in the ethanol extract.
In a clinical study, E. tectorum was tested for irritancy in twenty subjects.The results indicated that this plant had a mild irritant activity.Nevertheless, when tested in cream formulation it showed no skin irritation [30].Another clinical study examined the antiwrinkle effects of E. tectorum in twenty-six Caucasian females with Fitzpatrick skin phototypes I-III.It was concluded that the test product, compared to a placebo control, was effective in decreasing the wrinkle depth after 28 days of use with an application rate of two times per day [30].

Conclusions
The present review described thoroughly all the existing knowledge and research advances of the genus Elegia L. It focused on highlighting the importance of this genus as a major component of the fynbos biome, as well as its integral role in the cultural practices and everyday life of locals.Furthermore, taking also in consideration the recent results on the anti-wrinkle effects of E. tectorum, this overview unveiled the promising role of Elegia spp. as potential medicinal plants of South Africa with rich bioactive phytochemical content.
As a result, this study could be a stimulus for further research of the Elegia genus or even the entire Restionaceae family.In addition, it could be used as a guide for scientists in need of uncharted species that have not yet been fully explored.The fact that no Elegia species has been used traditionally as a medicinal plant should not be a prohibitive factor since scientists today have the necessary tools to unveil the hidden treasure of novel specialized metabolites of species that may have eluded human curiosity and history up until today.The research that has been conducted for the Elegia genus is very limited.Though, the results which are summarized herein clearly indicate that these plants could be a promising source and very beneficial for the local population and economy.Further studies should be carried out to acquire a better understanding on the phytochemistry and the pharmacological properties of the Elegia species.

Table 1 .
The number of searches/hits for each keyword.

Table 2 .
All species of the genus Elegia L. and their previous botanical names.

Table 3 .
Specialized natural products present in species of genus Elegia L.