Chemopreventive Activity of 80% Methanol Leaf Extract of Vernonia auriculifera Hiern (Asteraceae) Against Dimethylhydrazine-Induced Colorectal Carcinogenesis in Rats

Abstract

Background

Vernonia auriculifera Hiern (Asteraceae) is among Ethiopian herbal medicines that are traditionally used to treat skin and gastrointestinal cancers. In this study, the chemopreventive potential of Vernonia auriculifera leaf extract in dimethylhydrazine (DMH)-induced colorectal carcinogenesis in rats was investigated.

Methods

Rats were assigned to nine groups (normal, positive, and negative control groups, and three pre- and three post-initiation groups). Except for the normal control group (administered with 1 mL/100 g distilled water), the remaining eight groups were given DMH (20 mg/kg) intraperitoneally (ip) for 15 consecutive weeks to induce colorectal tumours. The extract was given orally to the pre-initiation and post-initiation groups at doses of 100, 200, and 400 mg/kg before and after the induction of cancer, respectively. The positive control group was treated with aspirin (60 mg/kg/day) orally for the whole experimental period. Parameters including body weight, average tumour number, size, progression, incidence, total cholesterol, serum total protein, and triglyceride levels were determined. The cytotoxic activity of the extract in Caco-2 cells was evaluated using the MTT assay, and the antioxidant activity of the extract was also assessed using 2.2-diphenyl-1-picrylhydrazine (DPPH) and reducing power methods. Moreover, total phenol and flavonoid contents were determined using appropriate methods.

Results

Rats treated with the extract showed a lower incidence of up to 50% in the pre-initiation higher dose, average number (p<0.05),and size (p<0.05) of tumours compared to untreated rats. It also inhibited colorectal cancer-associated increases in serum total cholesterol and triglycerides. The extract’s IC₅₀ value in the MTT assay was found to be higher than 200 µg/mL. The extract had an IC₅₀ of 74.88 ± 0.86 µg/mL and 84.69 ± 2.02 µg/mL in the reducing power and DPPH assays, respectively. Total flavonoid and phenol contents were 14.51 ± 0.41 mg quercetin acid equivalent/gm and 47.37 ± 0.72 mg gallic acid equivalent/gm of the crude extract, respectively.

Conclusion

The findings collectively indicated that the leaves of V. auriculifera possess chemopreventive activity, probably mediated through antioxidant mechanisms, which supports the traditional claim.

Keywords:

• antioxidant
• cytotoxicity
• colorectal cancer
• pre-initiation
• post-initiation
• Vernonia auriculifera

Abbreviations

ASA, Acetyl salicylic acid; CRC; Colorectal Cancer, DMH; 1, 2-dimethylhydrazine.

Ethical Approval

The experimental protocol was approved by the school of pharmacy institutional review board with Reference No. ERB/SOP/151/12/2017.

Acknowledgments

The authors acknowledge Addis Ababa University and staff members of School of Pharmacy for funding the research and for technical assistance respectively. This manuscript is a part of the first author’s thesis archived at the Addis Ababa University repository.

Disclosure

The authors report that they have no conflicts of interest.

Additional information

Funding

A thematic research grant (TR/35/2015) from Addis Ababa University funded this research.