7-Methyljuglone (7-MJ) is a pure compound isolated from the roots of Euclea natalensis A. DC., a shrub indigenous to South Africa. It exhibits significant promise as a potential treatment for the highly communicable disease tuberculosis (TB), owing to its effective antimycobacterial activity against Mycobacterium tuberculosis. Despite its potential therapeutic benefits, 7-MJ has demonstrated in vitro cytotoxicity against various cancerous and non-cancerous cell lines, raising concerns about its safety for consumption by TB patients. Therefore, this review focuses on exploring the potential of poly-(lactide-co-glycolic) acid (PLGA) nanoparticles as a delivery system, which has been shown to decrease in vitro cytotoxicity, and 7-MJ as an effective antimycobacterial compound.

Background/Objectives: Loading of natural products into poly-(lactide-co-glycolic) acid (PLGA) nanoparticles as drug delivery systems for the treatment of diseases, such as tuberculosis (TB), has been widely explored. The current study investigated the use of PLGA nanoparticles with 7-methyljuglone (7-MJ), an active pure compound, isolated from the roots of Euclea natalensis A. DC. Methods: 7-MJ as well as its respective PLGA nanoparticles were tested for their antimycobacterial activity against Mycobacterium smegmatis (M. smegmatis), drug-susceptible Mycobacterium tuberculosis (M. tuberculosis) (H37Rv), and multi-drug-resistant M. tuberculosis (MDR11). The cytotoxicity of 7-MJ as well as its respective PLGA nanoparticles were tested for their cytotoxic effect against differentiated human histiocytic lymphoma (U937) cells. Engulfment studies were also conducted to determine whether the PLGA nanoparticles are taken up by differentiated U937 cells. Results: 7-MJ has been shown to have a minimum inhibitory concentration (MIC) value of 1.6 µg/mL against M. smegmatis and multi-drug-resistant M. tuberculosis and 0.4 µg/mL against drug-susceptible M. tuberculosis. Whilst promising, 7-MJ was associated with cytotoxicity, with a fifty percent inhibition concentration (IC₅₀) of 3.25 µg/mL on differentiated U937 cells. In order to lower the cytotoxic potential, 7-MJ was loaded into PLGA nanoparticles. The 7-MJ PLGA nanoparticles showed an 80-fold decrease in cytotoxic activity compared to free 7-MJ, and the loaded nanoparticles were successfully taken up by differentiated macrophage-like U937 cells. Conclusions: The results of this study suggested the possibility of improved delivery during TB therapy via the use of PLGA nanoparticles.

Heteropyxis natalensis is a hardy semi-deciduous tree that lacks thorns and is located along the eastern coastline and central regions of South Africa. Characteristics of the tree are that it has a mottled and flaking bark and can grow up to 15 m. The leaves of the tree are waxy and shiny with a pale green colour and a strong lavender fragrance when crushed. The ethnobotanical usage of the tree includes pain relief, anti-infection and blood purification. The essential oil produced from the leaves of H. natalensis has been studied extensively, and it has yielded compounds such as linalool and myrcene. Extracts from the leaves have shown antibacterial, antifungal, antioxidant, anti-inflammatory, pro-inflammatory and anticancer activities in laboratory trials.

Pelargonium graveolens is a resilient, perennial shrub with sizable, velvety leaves that emit a potent rose-scented fragrance. It highlights eye-catching umbels of pinkish-white flowers. The aromatic leaves of this plant produce geranium oil. This essential oil is extensively used in cosmetics for its abilities such as removing dead skin cells, firming the skin, stimulating and generating new skin cells and reducing ageing signs. It is also used in pharmacology for its anti-inflammatory and antiseptic abilities. Both geranium essential oil and rose geranium essential oil are derived from distinct varieties of the P. graveolens plant species. These essential oils are comparable in composition and properties, rendering both equally advantageous for well-being. Rose geranium essential oil features a slightly more floral aroma, reminiscent of the scent of roses. In traditional medicine, the roots and aerial plant parts of the Pelargonium species are used in remedies for treating wounds, fever, sore throats and abscesses. Pelargonium graveolens has also been investigated for antibacterial, antifungal, antioxidant and anticancer activity as well as properties such as enzyme inhibition and photo-protectivity.

Carpobrotus dimidiatus is a sturdy, trailing plant characterised by succulent, green, three-sided leaves. It can spread across extensive areas, forming a resilient ground cover that can withstand drought and salt exposure. Its large, glossy, mauve flowers emerge individually on more or less upright flowering branches. The genus, Carpobrotus, is associated with the plant’s fruit and originates from the Greek words karpos and brotas, which signify fruit and edible, respectively. The ethnobotanical usage of C. dimidiatus includes juicing the leaves for wound healing, burns and toothache. The leaves of this plant have been shown to contain flavonoids and condensed tannins, especially catechol tannins. It has been reported that extracts of C. dimidiatus leaves exhibited antidiabetic, anti-inflammatory and antioxidant activities.