HELICHRYSUM CYMOSUM (L.) D.DON (ASTERACEAE): MEDICINAL USES, CHEMISTRY, AND BIOLOGICAL ACTIVITIES

Helichrysum cymosum is a valuable and well-known medicinal plant in tropical Africa. The current study critically reviewed the medicinal uses, phytochemistry and biological activities of H. cymosum. Information on medicinal uses, phytochemistry and biological activities of H. cymosum, was collected from multiple internet sources which included Scopus, Google Scholar, Elsevier, Science Direct, Web of Science, PubMed, SciFinder, and BMC. Additional information was gathered from pre-electronic sources such as journal articles, scientific reports, theses, books, and book chapters obtained from the University library. This study showed that H. cymosum is traditionally used as a purgative, ritual incense, and magical purposes and as herbal medicine for colds, cough, fever, headache, and wounds. Ethnopharmacological research revealed that H. cymosum extracts and compounds isolated from the species have antibacterial, antioxidant, antifungal, antiviral, anti-HIV, anti-inflammatory, antimalarial, and cytotoxicity activities. This research showed that H. cymosum is an integral part of indigenous pharmacopeia in tropical Africa, but there is lack of correlation between medicinal uses and existing pharmacological properties of the species. Therefore, future research should focus on evaluating the chemical and pharmacological properties of H. cymosum extracts and compounds isolated from the species.

a critical appraisal of the existing ethnomedicinal value, phytochemistry and biological activities of H. cymosum, as well as exploring the potential of the species as herbal medicine in tropical Africa.

BOTANICAL DESCRIPTION OF H. CYMOSUM
In South Africa, H. cymosum is known as gold carpet or yellow-tipped strawflower in English, goute tapyt in Afrikaans, and impepho in isiXhosa or Zulu [65]. H. cymosum is divided into two subspecies, H. cymosum subsp. cymosum and H. cymosum subsp. calvum Hilliard [65,69]. These two subspecies are differentiated on the basis that the head of subsp. cymosum has 6-20 flowers, fimbrils are more than twice as long as the ovary, and the pappus is copious [65,70]. While the head of subsp. calvum has 4-7 flowers, fimbrils are about as long as the ovary and the pappus is wanting [65,70]. In South Africa, subsp. calvum is shorter, ranging in height from 15 to 55 cm and has been recorded at an altitude ranging from 1200 to 3170 m above sea level [69]. The subsp. cymosum is taller than subsp. calvum, with height ranging from 10 to 180 cm and has been recorded at an altitude ranging from 5 to 2010 m above sea level [69]. However, most ethnobotanical and ethnopharmacological literature does not separate H. cymosum into specific subspecies but rather to H. cymosum sensu lato, and this is the approach that has been adopted in this study. There are four synonyms associated with H. cymosum and these include Gnaphalium cymosum L., G. serratum L., G. tricostatum Sieber ex DC., Helichrysum infaustum J.M. Wood and M.S. Evans var. discolor Moeser, and Lepiscline cymosa Cass [69,70].
H. cymosum is a well-branched spreading, perennial dwarf shrub with thin grayish-white woolly branches densely covered with leaves and becoming pedunculoid upward. The leaves are variable in shape and size, becoming smaller and more distant upward. The leaves are elliptic-oblong or linear-oblong in shape, the apex is acute, sometimes acuminate, mucronate, slightly narrowed, and clasping at the base [65,70]. The leaf margins are flat or subrevolute, upper surface covered in thin silvery gray and paper-like hairs, while the lower surface has white-woolly hairs. The flower heads are disciform,

Antibacterial activities
Sindambiwe et al. [72] [89,94]. Reddy [85] evaluated antibacterial activities of acetone and methanol extracts of aerial parts of H. cymosum as well as essential oils isolated from the species against E. coli, Yersinia enterocolitica, Klebsiella pneumoniae, S. aureus, and B. cereus using disc diffusion assay with ciprofloxacin (0.01 mg/ml) as a positive control. The acetone and methanol extracts exhibited activities against S. aureus and B. cereus with zone of inhibition of 7 and 5 mm, respectively, and MIC value of <0.25 mg/ml exhibited against both pathogens. The positive control exhibited zone of inhibition of 6 mm and MIC value of 0.0003 mg/ml [85].

Antioxidant activities
François et al. [95] evaluated the antioxidant activities of essential oil isolated from the leaves of H. cymosum using 2,2-diphenyl-1picrylhydrazyl (DPPH) free radical scavenging assay with butylated hydroxytoluene as a positive control. The extract exhibited activities with SC 50 (concentration of sample required to scavenge 50% of DPPH radicals) value of 6.3 g/l which was less than the value of the positive control which exhibited value of 7.0 mg/l [95].

Antifungal activities
Van Vuuren et al. [89] and Van Vuuren [94] evaluated the antifungal activities of acetone extract of aerial parts of H. cymosum, essential oil and compound helihumulone isolated from the species against Cryptococcus neoformans and Candida albicans using microdilution technique with amphotericin B as a positive control. The extract, essential oil and compound helihumulone exhibited activities with MIC values ranging from 0.03 to 4.0 mg/ml [89,94]. François et al. [95] evaluated the antifungal activities of essential oil isolated from the leaves of H. cymosum against Penicillium oxalicum using microdilution technique with amphotericin B as a positive control. The extract showed activities with 54.7% inhibition starting from 2.5 to 5 mg/ml [95]. Runyoro et al. [98] evaluated the antifungal activities of the essential oils isolated from H. cymosum against C. albicans using the bioautography agar overlay method with amphotericin B (0.01 µg) as a positive control. The extract showed activities with zone of inhibition ranging from 6 to 8.5 mm while the positive control exhibited zone of inhibition of 14.2 mm [98].

Anti-inflammatory activities
Stafford et al. [74] evaluated the anti-inflammatory activities of aqueous and ethanol extracts of whole plant parts of H. cymosum using the cyclooxygenase (COX-1) inhibition assay. The COX-1 inhibition exhibited by aqueous and ethanol extract was 52.0% and 100.0%, respectively [74].

Antimalarial activities
Van Vuuren et al. [89] evaluated the antimalarial activities of acetone extract of aerial parts of H. cymosum, essential oil and compound helihumulone isolated from the species using the [G-3 H] hypoxanthine incorporation assay using Plasmodium falciparum as the test organism with chloroquine and quinine as positive controls. The extract, essential oil and compound helihumulone showed activities, exhibiting half maximal inhibitory concentration (IC 50 ) values of 60.8 μg/ml, 1.3 μg/ml and 14.9 μg/ml, respectively. The positive controls exhibited IC 50 values ranging from 0.09 to 0.1 μg/ml [89].

CONCLUSION
In this review, the medicinal uses, phytochemistry, biological and toxicity activities of different extracts, and compounds of H. cymosum have been summarized. The diverse medicinal uses of H. cymosum and the preliminary phytochemical and ethnopharmacological

AUTHOR'S CONTRIBUTIONS
The author declares that this work was done by the author named in this article.

CONFLICTS OF INTEREST
The author declares that he has no conflict of interest.