**6. Cytotoxic activity of Melastomaceae**

The cytotoxic effect of the ethyl acetate fraction from *Melastoma malabathricum* in human breast and lung cancer cell lines (MCF-7 and A549) was studied by using an MTT assay. Results showed that MCF-7 and A549 cells undergo secondary necrosis 24 hours post-treatment with *M. malabathricum* extract [66]. Another observation showed that after 72 h of treatment, the *M. malabathricum* leaves extract exhibited important anticancer activity in the MCF-7 (IC50: 7.14 μg/mL) cell line, although the methanol and chloroform extract from the flowers had modest activities in MCF-7 (IC50: 33.63 μg/mL and 45.76 μg/mL) cell line [67]. In addition, Zakaria et al. studied the in vitro antiproliferative activity of various extracts (aqueous, chloroform, and methanol extracts) from *M. malabathricum*. The aqueous extract was found to be potent inhibitor of Caov-3 (IC50: 58 μg/mL), HL-60 (IC50: 58 μg/mL) cell lines, whereas CHCl3 extract showed antiproliferative activity toward Caov-3 (IC50: 34 μg/mL), HL-60 (IC50: 96 μg/ mL), and CEM-SS (IC50: 22 μg/mL) cell lines. The methanol extract established antiproliferative activity in more cell lines, such as MCF-7 (IC50: 87 μg/mL), HeLa (IC50: 88 μg/ mL), Caov-3 (IC50: 41 μg/mL), HL-60 (IC50: 13 μg/mL), CEM-SS (IC50: 30 μg/mL), and MDA-MB-231 (IC50: 59 μg/mL) cancer cell lines [68]. In 2019, Isnaini et al. studied the quercetin and kaempferol level in *M. malabathricum* ethanolic fruit extract. The analysis was done by HPLC MS/MS. In comparison to kaempferol (43.52 μg/g), quercetin (67.78 μg/g) had a greater concentration in the test sample. They also compared the extract to quercetin in terms of antioxidant and cytotoxic properties. The authors concluded that the extract exhibits antioxidant (IC50: 16.82 ± 0.24 ppm) and cytotoxic properties (LC50: 313.44 ppm) which may be attributed to the presence of quercetin [69]. The compounds such as flavonoids, naringenin, and kaempferol-3-O-(2′′,6′′-di-O*p*-trans-coumaroyl)glucoside, isolated from the flower of *M. malabathricum*, have been proved to be the potent inhibitor of MCF7 with IC50 values of 0.28 μM and 1.3 μM [70].

**Figure 4.**

*Cytotoxic compounds from* Melastoma malabathricum*.*

In another cytotoxic study by Hamid et al., the *M. malabathricum* leaves extract showed inhibitory effects on the MDA-MB-231 cell line after 48 and 72 h treatments [71]. The chemical structures of some cytotoxic compounds are shown in **Figure 4**.
