The utilization of plants in cancer prevention is driven by the necessity to reverse the adverse effects of chemotherapy and enhance the survival rates of patients’ post-surgery. The efficacy of plant-derived cancer agents in impeding cancer cell proliferation in specific bodily regions has been demonstrated (Zaid et al., 2012). For instance, the onion plant Allium cepa L has been found to be effective in inhibiting the growth of breast cancer cells by blocking the accumulation of fatty acids in the adipose tissues (Y. Wang et al., 2012). Another in vitro study also observed the anti-tumor effect of the aloe vera plant in both breast and cervical carcinoma cell lines (HeLa). The study’s findings indicated that exposure to aloe vera compounds led to the death of cancerous cells, while having no effect on normal cells (Ahmed & Husain, 2014).

The incorporation of flora, namely plants, herbs, and vegetables, into an individual’s dietary regimen has been demonstrated to exert a substantial influence on the probability of contracting cancer, in comparison to an individual with an inadequate diet. Ahmad et al. (2017) posit that in the nascent stages of cancer, it is feasible to arrest its progression, impeding its dissemination to other cells and halting its growth (Ahmad et al., 2017). This assertion is supported by the findings of Aung et al. (2017), who discovered that Calligonum Comosum extracts exert a substantial impact on the latency of hepatocellular carcinoma cells. The use of herbal-based medicines has been proposed as a highly effective cancer prevention strategy due to their potential to mitigate the likelihood of drug interactions, which can compromise the efficacy of combination therapy in addressing cancerous conditions. In comparison to synthetic anti-cancer drugs, natural options are often more cost-effective, readily available, straightforward in formulation, and characterized by a low incidence of adverse side effects (Ahmad et al., 2017).

Malaysian Plants that Have Anti-Cancer Properties

In Malaysia, the primary focus on herbal remedies and plant-based treatments for cancer prevention and treatment is largely driven by the country’s abundant rainforests (Mainasara et al., 2018). Local communities have traditionally utilized potent herbs in the treatment of minor malignancies, and at the pharmaceutical level, there has been a growing incorporation of herbal and plant-extract based medications in cancer treatment (Rahman, 2016). While most of the plants identified as having anti-cancer properties have yet to be fully commercialized, they have been effectively used in treating cancer patients with success (Hashim et al., 2016). The combination of plant-derived anti-cancer drugs has been shown to reduce the likelihood of drug resistance in patients. This is due to the plant extracts’ capacity to impede ATP binding cassette (ABC) transporters in conjunction with multidrug resistance proteins (MRP-s), thereby enhancing the efficacy of treatment in patients (Shabani, 2016). A multitude of studies have identified the chemoprotective and anticarcinogenic properties of plants in the treatment of cancer, a subject that will be addressed in the ensuing discussion.

Goniothalamus Umbrosus

The Kenerak plant (G. umbrosus) is a species of plant that is native to Malaysia. It has been utilized in the field of pharmaceuticals for its benefits in maternal health care and general wellbeing. However, research has identified specific species of this plant that contain styryl-lactones and acetogenins, which have been shown to have toxic effects on various forms of cancer, including colon, breast, pancreas, and kidney cancers (Ghazali et al., 2016).

Furthermore, styryl-lactones from the G. umbrosus species have been identified as effective inducers of apoptosis in mammalian and cancer cells (Arbyn et al., 2020). Ethyl acetate, a compound derived from the G. umbrosus plant, has demonstrated significant potential in the inhibition of cancer growth and spread in breast cancer cells (MCF7) (Arbyn et al., 2020). Following treatment with this compound, a mortality of the cancer cells in the breast was observed.  Consequently, there has been a surge in research endeavors exploring the potential of employing plant extracts in the treatment of breast cancer (Ibrahim et al., 2019).

Typhonium Flagelliforme

In Malaysia, the plant is referred to as Keladi Tikus, and it is employed as a derivative drug for the treatment of various forms of cancer. This herbaceous plant, which often grows up to 30 centimeters in height, is utilized as a medicinal agent. The plant’s juice is orally administered after the entire plant is crushed (Setiawati et al., 2016). In vitro studies have demonstrated the efficacy of an extract of Typhonium flagelliforme in treating NCI-H23 human lung carcinoma, T-47D human breast carcinoma cell lines, and P388 murine leukemia cells (Setiawati et al., 2016). Moreover, the plant extract has been utilized in Malaysia for the treatment of malignancies.Notwithstanding the plant’s anti-cancer properties, clinical trials have been stagnant. The stem and leaves of this tuber plant have been found to contain more potent anti-cancer agents (Sianipar & Purnamaningsih, 2018).

Clinacanthus Nutans

The plant is known in the local context as Sabah snake grass in Malaysia, and it is classified within the family of Acanthaceae (Alam et al., 2016). It is regarded as one of the most ancient native herbs, originating from tropical Asia. It is utilized as a conventional treatment agent in Malaysia, China, and Thailand (Ghantous & Abu Elnaaj, 2017). The plant has been employed to treat various ailments, including animal bites, skin irritations, diabetes, and the Herpes simplex virus (HSV). However, studies have demonstrated that the chloroform extracts from this plant exhibit potent effects in destroying anti-cancer cells in vitro, including HepG2, IMR32, NCL-H23, SNU-1, HeLa, LS-174T, K562, and Raji cells (Ng et al., 2017). Furthermore, the leaves of this plant have been shown to possess significant antiviral and anti-inflammatory properties (Teoh et al., 2017). In addition, they have been identified as effective in inhibiting neutrophil response and the formation of edema. Emerging evidence suggests that C. nutans holds significant anti-tumorigenic effects, which are vital components of anti-cancer growth (Huang et al., 2015). Studies have indicated that the chloroform extract of C. nutans leaves is a potent agent capable of eliminating free radicals and preventing the growth of cancerous cells in culture. Yakop et al. (2018) further suggested that these agents could serve as an effective alternative to chemotherapy for individuals at risk of developing cancer. 

Plant-Derived Anti-HIV Agents in Clinical Use

Plants are increasingly being recognized as effective in the development of anti-HIV agents based on their diverse medicinal value. While there are still limited studies to discuss plants that prevent one from being infected with HIV, there is evidence that the inclusion of medicinal herbs and plants help in patients who have drug resistance, toxicity, and other co-morbidities. For example, when an HIV-positive patient eats organic foods, their immune system is strengthened and they have fewer health complications (Prinsloo et al., 2018).

It is common for HIV patients to have liver and kidney toxicity. However, when these patients took herbal medicines and herbs, they were able to get rid of the side effects of toxicity. There was an improvement in their liver and kidney health (Khan, 2017).

Adansonia digitata, Terminalia sericea, Hypoxis Hemerocallidea, and Moringa oleifera have been shown to inhibit HIV-1 reverse transcriptase. HIV patients who used these medicinal plants as a complementary therapy to their HIV treatment regimen were found to have a lower viral load and an increase in their CD4 count (Habibi et al., 2019). However, it is important to note that there has been resistance in several countries to the full adoption of herbal medicine for the treatment of HIV. A common reason for this is that there is still ongoing research into how the medicinal plants would interact with synthetic drugs and whether there would be any side effects (Jayasundar et al., 2019).

Plants are also used to treat opportunistic infections that are common in patients infected with HIV/AIDS. The opportunistic infections include cancer, tuberculosis, skin and oral infections, and these are effectively treated with plants and herbs in HIV patients. The Moringa plant is commonly used to treat respiratory infections in HIV patients. It contains a similar structure to nucleoside analogues found in synthetic antiretroviral drugs (Kurapati et al., 2016).

Secondary symptoms of HIV/AIDS are also effectively managed through the consistent use of medicinal plants and herbs. This is seen in the case of tobacco plants, which produce monoclonal antibodies that are essential for supporting the compromised immune system of HIV patients. Since the disease affects and weakens the immune system, the plants used would contain high nutritional and pharmaceutical value (Okay & Sezgin, 2018).

Natural products that have been discovered to contain significant anti-HIV compounds include calanolides (coumarins), ursolic and betulinic acids (triterpenes), baicalin (flavonoid), polycitone A (alkaloid), and lithospermic acid (phenolic compound). However, they are all still in clinical trials and have not yet been commercialized. These plant-derived drugs have been found to have similar structures within the nucleoside reverse transcriptase inhibitor (NRTI) and non-nucleoside reverse transcriptase inhibitor (NNRTI) classes (Boukandou Mounanga et al., 2018).