Catharanthus roseus (L.) G. Don is a herbal plant traditionally used by local populations in India, South Africa, China and Malaysia to treat diabetes. The present study reports the in vitro antioxidant and antidiabetic activities of the major alkaloids isolated from Catharanthus roseus (L.) G. Don leaves extract. Four alkaloids—vindoline I, vindolidine II, vindolicine III and vindolinine IV—were isolated and identified from the dichloromethane extract (DE) of this plant’s leaves. DE and compounds I–III were not cytotoxic towards pancreatic β-TC6 cells at the highest dosage tested (25.0 µg/mL). All four alkaloids induced relatively high glucose uptake in pancreatic β-TC6 or myoblast C2C12 cells, with III showing the highest activity. In addition, compounds II–IV demonstrated good protein tyrosine phosphatase-1B (PTP-1B) inhibition activity, implying their therapeutic potential against type 2 diabetes. III showed the highest antioxidant potential in ORAC and DPPH assays and it also alleviated H₂O₂-induced oxidative damage in β-TC6 cells at 12.5 µg/mL and 25.0 µg/mL.

Three isoflavanoids, isovestitol (1), medicarpin (2), and sativan (3), along with another known compound, betulinic acid (4), were isolated from the root of Sesbania grandiflora. The structures of the isolated compounds were characterised by means of spectroscopic techniques (UV, IR, MS, ¹H- and ¹³C-NMR, DEPT, COSY, HMQC, HMBC, and MS analysis). All the tested compounds 1–4 exhibited antituberculosis activity against Mycobacterium tuberculosis H37Rv, with MIC values of 50 µg/mL for compounds 1–3, and 100 µg/mL for compound 4, whereas, the methanol extract exhibited antituberculosis activity of 625 µg/mL. This is the first report on the occurrence of isoflavonoids in this plant and their antituberculosis activity.

In this study, a new apoptotic monoterpenoid indole alkaloid, subditine (1), and four known compounds were isolated from the bark of Nauclea subdita. Complete ¹H- and ¹³C- NMR data of the new compound were reported. The structures of isolated compounds were elucidated with various spectroscopic methods such as 1D- and 2D- NMR, IR, UV and LCMS. All five compounds were screened for cytotoxic activities on LNCaP and PC-3 human prostate cancer cell-lines. Among the five compounds, the new alkaloid, subditine (1), demonstrated the most potent cell growth inhibition activity and selective against LNCaP with an IC₅₀ of 12.24±0.19 µM and PC-3 with an IC₅₀ of 13.97±0.32 µM, compared to RWPE human normal epithelial cell line (IC₅₀ = 30.48±0.08 µM). Subditine (1) treatment induced apoptosis in LNCaP and PC-3 as evidenced by increased cell permeability, disruption of cytoskeletal structures and increased nuclear fragmentation. In addition, subditine (1) enhanced intracellular reactive oxygen species (ROS) production, as reflected by increased expression of glutathione reductase (GR) to scavenge damaging free radicals in both prostate cancer cell-lines. Excessive ROS could lead to disruption of mitochondrial membrane potential (MMP), release of cytochrome c and subsequent caspase 9, 3/7 activation. Further Western blot analyses showed subditine (1) induced down-regulation of Bcl-2 and Bcl-xl expression, whereas p53 was up-regulated in LNCaP (p53-wild-type), but not in PC-3 (p53-null). Overall, our data demonstrated that the new compound subditine (1) exerts anti-proliferative effect on LNCaP and PC-3 human prostate cancer cells through induction of apoptosis.

1’-(S)-1’-Acetoxychavicol acetate (ACA) isolated from the Malaysian ethno-medicinal plant Alpinia conchigera Griff. was investigated for its potential as an anticancer drug. In this communication, we describe the cytotoxic and apoptotic properties of ACA on five human tumour cell lines. Data from MTT cell viability assays indicated that ACA induced both time- and dose-dependent cytotoxicity on all tumour cell lines tested and had no adverse cytotoxic effects on normal cells. Total mortality of the entire tumour cell population was achieved within 30 hrs when treated with ACA at 40.0 µM concentration. Flow cytometric analysis for annexin-V and PI dual staining demonstrated that cell death occurred via apoptosis, followed by secondary necrosis. The apoptotic effects of ACA were confirmed via the DNA fragmentation assay, in which consistent laddering of genomic DNA was observed for all tumour cell lines after a 24 hrs post-treatment period at the IC₅₀ concentration of ACA. A cell cycle analysis using PI staining also demonstrated that ACA induced cell cycle arrest at the G₀/G₁ phase, corresponding to oral tumour cell lines. In conclusion, ACA exhibits enormous potential for future development as a chemotherapeutic drug against various malignancies.