Screening of natural products for therapeutic activity against solid tumors
Bassem S El-Menshawi1, Walid Fayad, Khaled Mahmoud
1Department of Pharmacognosy, Pharmaceutical Sciences Division, National Research Centre, Dokki, Giza 12622, Egypt.
Abstract:
Most of the currently used cancer therapeutics are natural products. These agents were generally discovered based on their toxicity to tumour cells using various bioassays. Although the exact mechanisms of action of the most commonly used cancer therapeutics such as anthracyclins, podophyllotoxins and camptothecin are incompletely understood, it is becoming increasingly clear that these agents often show complex modes of action at the cellular level, interacting with numerous targets. Such complex modes of action may be the very reason for clinical efficacy. For discovering new cytotoxic anticancer drugs sophisticated screening methods were used. The principles of such screening projects conducted, using collections of purified natural products or extracts from plants have been described. By performing simple but robust prescreening tests such as the brine shrimp assay, bioactive extracts can be identified. Extracts (65) prepared from a collection of Egyptian plants were identified that showed cytotoxity on HepG2 cells. Interestingly, 22 (33%) of these raw extracts, induced > 2-fold induction of caspase-cleavage activity in a colon carcinoma cell line, consistent with induction of apoptosis. Only a fraction of the diversity of the biosphere has been tested for biological activity and novel cancer therapeutics remains to be discovered.
Insights
Natural products are key cancer therapeutics, often with complex mechanisms. Screening Egyptian plant extracts identified cytotoxic compounds, with many inducing apoptosis, highlighting potential for new cancer drug discovery.
Area of Science:
- Natural product chemistry
- Cancer biology
- Drug discovery
Background:
- Many current cancer therapeutics are derived from natural products.
- Discovery of these agents typically relies on bioassays identifying compounds toxic to tumor cells.
- Complex mechanisms of action, involving multiple cellular targets, may contribute to the clinical efficacy of natural product-based cancer drugs.
Purpose of the Study:
- To describe principles for discovering novel cytotoxic anticancer drugs using natural product screening.
- To identify bioactive extracts from Egyptian plants with potential anticancer properties.
- To assess the induction of apoptosis by these plant extracts.
Main Methods:
- Utilized prescreening tests, such as the brine shrimp assay, to identify bioactive extracts.
- Prepared and tested 65 raw extracts from a collection of Egyptian plants for cytotoxicity against HepG2 cells.
- Assessed the induction of caspase-cleavage activity as an indicator of apoptosis in a colon carcinoma cell line.
Main Results:
- Identified 65 plant extracts exhibiting cytotoxicity against HepG2 cancer cells.
- Found that 22 (33%) of these extracts significantly induced apoptosis, indicated by caspase-cleavage activity.
- Demonstrated that a small fraction of the biosphere's diversity has been explored for therapeutic potential.
Conclusions:
- Egyptian plant extracts represent a promising source for novel anticancer drug discovery.
- Apoptosis induction is a key mechanism by which some natural products exert their cytotoxic effects.
- Further exploration of natural product diversity is crucial for identifying future cancer therapeutics.
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