In vitro cytotoxic activity of medicinal plants from Nigeria ethnomedicine on Rhabdomyosarcoma cancer cell line and HPLC analysis of active extracts

A mangrove shrub grows at the edge of a creek in Ijebu, southwestern Nigeria. This is not a pharmaceutical lab or a clinical trial. It is just a plant that local healers have been using against cancer for generations. The hard question is whether it actually works — not in the sense of "does traditional medicine have cultural value," but in the precise, measurable, cell-killing sense that a cancer researcher would demand. Ogbole, Segun, and Adeniji decided to find out. The scale of the problem they were addressing matters. In 2015, there were approximately 17.5 million new cancer cases worldwide and 8.7 million cancer-related deaths. Nigeria, with roughly 20 percent of Africa's population, shouldered a substantial portion of that continental burden. One cancer in particular drove this study: rhabdomyosarcoma, the most common soft-tissue sarcoma in children and adolescents under 20. In the United States, its incidence runs at about five cases per million children per year, with more than half of all cases appearing in the first decade of life. In Nigeria, it strikes the pediatric population frequently and is a common cause of mortality in that age group. The drugs available to treat this cancer are imperfect. Existing chemotherapy agents carry persistent problems: poor selectivity and severe side effects. They do not discriminate cleanly between cancer cells and healthy ones, which limits how aggressively they can be used. This gap — between what oncologists need and what current drugs provide — is exactly where plant-derived medicine might step in. The World Health Organization estimates that 80 percent of people in developing nations depend on herbal medicine for primary health care. Nigeria has a vast flora of medicinal plants, many with cancer-fighting reputations that have never been rigorously tested. So, Ogbole and colleagues started with an ethnobotanical survey. Between May and September 2015, they interviewed traditional medical practitioners in the Ijebu region and recorded 90 plants used for cancer treatment. Bibliographic filtering narrowed that list to 31 species whose cytotoxic potential had never, or only partially, been evaluated. Those 31 became the test panel. The screening was two stages, and the logic is worth understanding because it shapes everything that follows. First came the brine shrimp lethality assay — a fast, cheap proxy for cytotoxicity. Tiny crustacean larvae called Artemia salina nauplii are exposed to serial dilutions of each extract, and after 24 hours, you count how many died. This does not tell you about cancer specifically, but it indicates whether a compound is biologically active at all. The key number is the LC50 — the concentration that kills 50 percent of the shrimp. All but one of the 31 extracts had LC50 values below 1000 micrograms per milliliter, meaning virtually everything in the panel showed some biological activity. One extract, from Eleusine indica, was the most potent brine shrimp killer, with an LC50 of 76.3 micrograms per milliliter. The positive control, the chemotherapy drug cyclophosphamide, came in at 101.3 micrograms per milliliter. Brine shrimp, though, are not cancer cells. The second stage was the MTT cytotoxicity assay — a standard cell-culture test that measures whether cells are metabolically active and, therefore, alive. The researchers used three cell lines: RD, a human rhabdomyosarcoma line representing the cancer target; Vero, a normal kidney cell line; and PNT2, a normal prostate cell line. The last two are the control surfaces — they allow you to test whether an extract is selectively toxic to cancer or just toxic to everything. Cells were exposed to extracts for 72 hours, and the result was a CC50 value: the concentration that cuts cell viability by half. Eleven of the 31 extracts met the American National Cancer Institute's preliminary criterion for crude-extract cytotoxicity, a CC50 below 30 micrograms per milliliter against RD cells. Two species stood well clear of the rest. Macaranga barteri — a plant in the Euphorbiaceae family — had a CC50 of 0.22 micrograms per milliliter on RD cells. Calliandra portoricensis, a legume, came in at 0.82 micrograms per milliliter. Cyclophosphamide, for reference, had a CC50 of 0.97 micrograms per milliliter in the same assay. So, the crude extracts from both plants were already outperforming an established chemotherapy drug in cancer cell killing. That's the headline. But it gets sharper. The team then fractionated the two top extracts — essentially separating them by chemical polarity to concentrate the active compounds. The dichloromethane fraction of Macaranga barteri, called DMB, and the ethyl acetate fraction of Calliandra portoricensis, called ECP, were taken forward. DMB produced a CC50 of 0.15 micrograms per milliliter on RD cells. ECP came in at 0.25 micrograms per milliliter. Against cyclophosphamide's 0.97, that translates to approximately six times greater activity for DMB and four times greater activity for ECP. These fractions weren't just marginally better than the drug. They were substantially more potent by any reasonable measure. Potency alone, though, isn't enough. A compound that kills cancer cells efficiently but destroys normal cells just as readily is not a drug candidate — it's a poison. This is where the selectivity index becomes critical. The selectivity index is the ratio of cytotoxicity against normal cells to cytotoxicity against the cancer cells. A high selectivity index means the compound preferentially kills the tumor. An index above 10 is classified as highly selective. DMB had a selectivity index of 13.7 against normal Vero cells. ECP had a selectivity index of 11.1 against PNT2 normal prostate cells. Cyclophosphamide's selectivity index, by comparison, was 5.4. DMB and ECP weren't just more potent — they were also more selective. They were hitting cancer cells approximately 13 and 11 times harder than normal cells, respectively, while cyclophosphamide was only hitting cancer cells about 5 times harder than normal ones. That combination — high potency and high selectivity — is exactly the profile researchers are looking for when screening for drug leads. It does not mean these fractions will become drugs. It means they are worth investigating. The natural next question is: what is actually in these fractions? To answer it, Ogbole and colleagues ran both DMB and ECP through high-performance liquid chromatography, which separates the chemical cocktail of a plant extract into individual peaks — each peak a distinct compound or compound class. DMB produced 19 peaks, with four dominating: three, five-dicaffeoylquinic acid, acteoside, kaempferol-7-O-glucoside, and bastadin 11. Each of these has a scientific record worth noting. Acteoside is a phenylpropanoid glycoside with documented anticancer, anti-inflammatory, and antimetastatic activities — it has been shown to exert antiestrogenic effects on breast cancer cells and to induce differentiation in leukemia cells. Kaempferol-7-O-glucoside is a flavonoid with reported antimicrobial and antioxidant properties. Bastadin analogues have shown cytotoxicity against T-cell lymphoma in vitro. Ohnishi and colleagues found that three, five-dicaffeoylquinic acid had stronger free-radical scavenging activity than vitamin E or vitamin C. The ECP fraction from Calliandra portoricensis told a different chemical story. Its major peaks matched neurolenin B, nigrosporolide, and trans-geranic acid. Neurolenin B has reported cytotoxicity against human small lung carcinoma in vitro and strong antimalarial activity against Plasmodium falciparum. Nigrosporolide is a 14-membered lactone previously noted for plant growth inhibitory activity. The chromatography data identifies suspects, not convicts. Ogbole and colleagues are careful about this. What it shows is which compounds are present in a fraction that is cytotoxically active. It does not prove that any one of those compounds is doing the killing. That determination requires isolating each compound individually and testing it in the same cell assays. Further work to confirm responsibility — and to potentially uncover entirely novel cytotoxic natural products — is ongoing. What the study does establish is a proof of concept for the ethnobotanical approach. Healers in the Ijebu region pointed toward plants. Rigorous laboratory testing confirmed that two of those plants — Macaranga barteri and Calliandra portoricensis — contain biologically active fractions that outperform a standard chemotherapy drug in cell culture while showing a high degree of cancer selectivity. In a landscape where new anticancer leads are slow and expensive to find, the ethnobotanical record — accumulated over centuries of observation — is a starting library that we've barely begun to explore. These two plants just earned a much closer look. This lecture was created by ennepō. Go to https://ennepo.ai to Discover, Create and Follow the latest research in your field. Read when you can. Listen when you want to.