The global management of diabetes mellitus (DM) involves the administration of recommended anti-diabetic drugs in addition to a non-sedentary lifestyle upon diagnosis. Despite the success recorded from these synthetic drugs, the traditional method of treatment using medicinal plants is increasingly accepted by the locals due to its low cost and the perceived no side effects. Helichrysum species are used in folk medicine and are documented for the treatment of DM in different regions of the world. This study reviews Helichrysum species and its compounds’ activities in the management of DM. An extensive literature search was carried out, utilizing several scientific databases, ethnobotanical books, theses, and dissertations. About twenty-two Helichrysum species were reported for the treatment of diabetes in different regions of the world. Among these Helichrysum species, only fifteen have been scientifically investigated for their antidiabetic activities, and twelve compounds were identified as bioactive constituents for diabetes. This present review study will be a useful tool for scientists and health professionals working in the field of pharmacology and therapeutics to develop potent antidiabetic drugs that are devoid of side effects.

Searsia is the more recent name for the genus Rhus, which contains over 250 individual species of flowering plants in the family Anacardiaceae. Several Searsia species are used in folk medicine and have been reported to exhibit various biological activities. Although known to exhibit different terpenoids and flavonoids, the chemistry of the Searsia genus is not comprehensively studied due to the structural complexity of the compounds. In this study, the extraction, isolation, and identification of secondary metabolites from three Searsia species (Searsia glauca, S. lucida, and S. laevigata) were conducted using chromatographic and spectroscopic techniques and afforded five known terpenes, viz., moronic acid (1), 21β-hydroxylolean-12-en-3-one (2), lupeol (11), α-amyrin (9), and β-amyrin (10), in addition to six known flavonoids, myricetin-3-O-β-galactopyranoside (3), rutin (4), quercetin (5), apigenin (6), amentoflavone (7), and quercetin-3-O-β-glucoside (8). The structural elucidation of the isolated compounds was determined based on NMR (1D and 2D) and comparison with the data in the literature. Biological assays, such as antioxidant and enzyme inhibition activity assays, were conducted on the plant extracts and the isolated compounds. The antioxidant capacities of hexane, dichloromethane, ethyl acetate, methanol, and butanol main extracts were investigated using ferric ion reducing power (FRAP), oxygen radical absorbance capacity (ORAC), and Trolox equivalent antioxidant capacity (TEAC) assays. The results showed high antioxidant activities for methanol and butanol extracts of the three plants. The isolated compounds were tested against alpha-glucosidase and alpha-amylase, and the results showed the potent activity of moronic acid (C1) (IC₅₀ 10.62 ± 0.89 and 20.08 ± 0.56 µg/mL, respectively) and amentoflavone (C7) (IC₅₀ 5.57 ± 1.12 µg/mL and 19.84 ± 1.33 µg/mL, respectively). Isolated compounds of and biological assays for S. glauca, S. lucida, and S. laevigata are reported for the first time.

Protea cynaroides (king protea) is a flowering plant that belongs to the Proteaceae family. This multi-stemmed shrub is the national flower of South Africa and has important economic and medicinal values. Traditionally, the main therapeutic benefits of this plant species include the treatment of cancer, bladder, and kidney ailments. There are very limited reports on the isolation of phytochemicals and their biological evaluation from P. cynaroides. In this study, the leaves of P. cynaroides were air-dried at room temperature, powdered, and extracted with 80% methanol followed by solvent fractionation (hexane, dichloromethane, ethyl acetate, and butanol). The ethyl acetate and butanol extracts were chromatographed and afforded four new (1–4) and four known (5–8) compounds, whose structures were characterized accordingly as 3,4-bis(4-hydroxybenzoyl)-1,5-anhydro-D-glucitol (1), 4-hydroxybenzoyl-1,5-anhydro-D-glucitol (2), 2-(hydroxymethyl)-4-oxo-4H-pyran-3-yl-6-O-benzoate-β-D-glucopyranoside (3), 3-hydroxy-7,8-dihydro-β-ionone 3-O-β-D-glucopyranoside (4), 4-hydroxybenzoic acid (5), 1,5-anhydro-D-glucitol (6), 3,4-dihydroxybenzoic acid (7), and 3-hydroxykojic acid (8). The structural elucidation of the isolated compounds was determined based on 1D and 2D NMR, FTIR, and HRMS spectroscopy, as well as compared with the available literature data. The tyrosinase inhibitory activities of the extracts and isolated compounds were also determined. According to the results, compounds 7 and 8 exhibited potent competitive tyrosinase inhibitory activity against L-tyrosine substrates with IC₅₀ values of 0.8776 ± 0.012 and 0.7215 ± 0.090 µg/mL compared to the control (kojic acid, IC₅₀ = 0.8347 ± 0.093), respectively. This study is the first chemical investigation of compounds 1–4 from a natural source and the first report of the biological evaluation of compounds 1–5 against the tyrosinase enzyme. The potent anti-tyrosinase activity exhibited by P. cynaroides constituents will support future exploration of the plant in the cosmetic field upon further biological and clinical investigations.

Dicerothamnus rhinocerotis (L.f.) Koekemoer, also known as rhinoceros bush and previously called Elytropappus rhinocerotis (L.f.) Less., is from the Asteraceae plant family. The plant is traditionally used to treat indigestion, stomach ulcers, influenza, and diarrhea. This study was aimed at investigating the phytochemistry, anti-glucosidase, anti-amylase, and anti-tyrosinase effects of D. rhinocerotis as research in this area is limited. The air-dried plant materials were macerated in 80% methanol (MeOH) and fractionated between hexane, dichloromethane (DCM), ethyl acetate (EtOAc), and butanol (BuOH). Column chromatography on silica gel was employed for the isolation of the compounds. A total of six compounds (1–6) were isolated from the fractions viz. acacetin (1), 15-hydroxy-cis-clerodan-3-ene-18-oic-acid (2), acacetin-7-glucoside (3), pinitol (4), apigenin (5), and β-sitosterol-3-O-glycoside (6). Compounds 2–4 and 6 are reported for the first time from this plant. Among the different fractions, the BuOH and EtOAc fractions had strong tyrosinase inhibitory activities with IC₅₀ values of 13.7 ± 1.71 and 11.6 ± 2.68 µg/mL, respectively, while among the isolated compounds, apigenin (5) had the strongest inhibitory activity, with an IC₅₀ of 14.58 µM, which competes favorably with Kojic acid (17.26 µM). The anti-glucosidase assay showed good activity in three of the fractions and compound 5, while the anti-amylase assays did not show significant inhibition activity.