The genus Helichrysum Mill comprises hundreds of species that are mostly flowering perennial shrubs. Some of these plants that belong to the Helichrysum species are used in traditional medicine to treat cough, back pain, diabetes, asthma, digestive problems, menstrual pain, chest pain, kidney disorders, skin disorders, wounds, open sores, among other conditions, but, only a few scientific studies are reported in the literature with sufficient information that validates the acclaimed folkloric benefits of these plants. Cytotoxicity, genotoxicity, anti-proliferative, anti-bacterial, anti-fungal, anti-viral, anti-HIV, anti-malarial, anti-ulcerogenic, anti-tyrosinase, anti-inflammatory, and anti-oxidant activities are reported of selected Helichrysum species of interest: H. petiolare, H. cymocum, H. foetidum, and H. pandurifolium Schrank, using scientific databases as well as electronic and print sources.
The genus Helichrysum Mill comprises distinctively of aromatic herbs and shrubs of the family Asteraceae . It has a worldwide distribution but is mainly found in Africa, with its highest diversity in South Africa, where approximately 245 of the 500 known species occur. Other areas of Helichrysum diversity include Europe, southwestern Asia, South India, Sri Lanka, Turkey, and Australia. For ease of identification, the southern African species are divided into 30 informal groups .
Plants of the Helichrysum genus have been in use for more than 2000 years for various folkloric purposes. The flowers of some members of this genus have a unique bright-yellow color that depicts their Greek language origins: “helios” and “chryos” which mean “sun” and “gold” respectively. In folkloric medicine, some Helichrysum plant parts are either consumed as teas or prepared as “burnt offering” smoke to disinfect the abodes of sick patients and to appeal for blessings from the ancestors in indigenous traditional practices . In general, plants of this genus are known to be used in traditional medicine for the treatment of many ailments, including liver disorders, gall bladder complications, cystitis, jaundice, stomach pain, allergies, infections, colds, cough, skin infections, inflammation, menstrual pain, asthma, arthritis, insomnia, diabetes mellitus, and for wound healing , most commonly, the scented leaves and flowers.
The therapeutic properties of the Helichrysum species are often attributed to their different constituent phytochemicals, especially the essential oils . In addition to the essential oils, plants in this species also contain such phytochemicals as terpenoids, phenolics and oxygenated compounds as secondary metabolites, including flavonoids, chalcones, phenolic acids, terpenes and essential oils, pyrone, benzofurans, and phloroglucinols . Thus, these plants are potential reservoirs of bioactive compounds for drug discovery and development. Hitherto, only limited biological effects of the Helichrysum phytochemicals have been reported including, the antioxidant, antifungal, anti-inflammatory, anti-bacterial, hepatoprotective, anti-proliferative and anti-diabetic activities .
So far, only a few of the many Helichrysum species have been studied; the best known Helichrysum species used traditionally to treat different ailments are H. cymosum , H. odoratissimum , H. petiolare and H. nudifolium . Only limited information is available in the literature on these plant species on their ornamental, industrial and pharmaceutical applications .
Essential oils (EOs) are the condensed or concentrated hydrophobic liquids that contain volatile chemical compounds derived from plants. The variety of compounds in EOs depends on such factors as the plant species, plant part used (leaves, fruits, roots), harvest period, environmental conditions (land fertility, humidity, temperature) and the extraction technique employed .
One distinct characteristic of the helichrysum genus is its aromatic nature and most of the species in this genus have been reported to be rich in essential oils (EOs) containing many compounds . Many EOs are prescribed as alternative medicine (in aromatherapy) based on the healing effects of their aromatic compounds . Monoterpenes, sesquiterpenes and diterpenes are some of the broad groups of compounds present in the EOs of most plants, including the helichrysum genus ; these compounds are largely responsible for the reported anti-fungal, anti-bacterial, anti-diabetic, anti-inflammatory, anti-ulcer, anti-cancer, anti-oxidant, anti-nociceptive, and anti-spasmodic properties associated with these plants (Table 1).
Table 1. The common phytochemical compounds present in the essential oils of selected Helichyrsum species.
|Helichrysum Species||Plant Parts||Compounds||Method of Analysis||Pharmacological Activity||References|
A growing Helichrysum petiolare plant  SANBI available online http://pza.sanbi.org/helichrysum-petiolare (accessed on 19 June 2021)
|Leaves||α-pinene (6.8%), 1, 8-cineole (22.4), p-cymene (9.8%) and β-caryophyllene (14%)||G.C.-M.S.||Anti-fungal, anti-inflammatory|||
|Whole plant||(E)-Longipinane (11.79%), trans-Geranylgeraniol (11.68%), Phytol (11.28%) Geranyllinalool (11.13%) and α-Eicosane (12.07%)||G.C.-M.S.||Anti-microbial, anti-inflammatory|||
A growing Helichrysum cymosum plant  SANBI available online: http://pza.sanbi.org/helichrysum-cymosum-subsp-cymosum (accessed on 19 June 2021)
|Leaves, Flowers||∆-3-carene (16.1%), β-caryophyllene (12.0%)||G.C., G.C.-M.S.||Anti-fungal|||
|Leaves, Flowers||(Z) -β- ocimene||G.C.-M.S.||-|||
|Leaves||α-pinene (12.4%), 1, 8-cineole (20.4%), β-caryophyllene (10.8%)||Anti-bacterial|||
A growing Helichrysum foetidum plant  SANBI available online http://pza.sanbi.org/helichrysum-foetidum (accessed on 19 June 2021)
|Leaves, flower||Β-pinene (3.1%), Trans-Sabiene hydrate (1.8%), 4-terpineol (3.1%), β-caryophyllene (2.5%)||G.C.-M.S.||Anti-microbial
A growing Helichrysum pandurifolium plant  iNaturalist. Available online: https://www.inaturalist.org/observations/23571154 (accessed on 19 June 2021)