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Antitumor activity of Pulsatilla koreana saponins and their structure-activity relationship
Seong-Cheol Bang1, Ji-Hyun Lee, Gyu-Yong Song
1SB Pharmaceutical Co., Chungnam, Korea.
Abstract:
Seventeen saponins isolated from the root of Pulsatilla koreana were examined for their in vitro cytotoxic activity against the human solid cancer cell lines, A-549, SK-OV-3, SK-MEL-2, and HCT15, using the SRB assay method, and their in vivo antitumor activity using BDF1 mice bearing Lewis lung carcinoma (LLC). The saponins 5-17, with a free acidic functional group at C-28 of aglycon, exhibited moderate to considerable cytotoxic activity, however, the saponins 1-4, esterified with a trisaccharide at C-28 of aglycon, did not exhibit cytotoxic activity (ED50; >300 microM). Among them, oleanolic acid 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->4)]-alpha-L-arabinopyranoside (10) exhibited the most potent cytotoxic activity (ED50; 2.56, 2.31, 1.57, 8.36 microM, respectively). In vivo test, hederagenin 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->4)]-alpha-L-arabinopyranoside (6, Inhibition Ratio, IR; 66.9%) exhibited more potent antitumor activity than taxol (IR; 35.8%) and doxorubicin (IR; 62.1%). Also, hedragenin 3-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside (17, IR; 50.3%) exhibited potent antitumor activity. These two saponins were identically comprised of a hederagenin aglycon moiety and a sugar sequence O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside at C-3 of the hederagenin, suggesting that the two elements are essential factors for the antitumor activity.
Insights
Pulsatilla koreana saponins show potent anticancer activity. Saponins with a free acidic group were cytotoxic, with specific compounds demonstrating significant in vitro and in vivo antitumor effects against various cancer models.
Area of Science:
- Natural Products Chemistry
- Pharmacology
- Oncology
Background:
- Pulsatilla koreana root is a traditional medicine source.
- Saponins are a diverse class of natural compounds with various biological activities.
- Cancer remains a major global health challenge, necessitating novel therapeutic agents.
Purpose of the Study:
- To investigate the cytotoxic and antitumor activities of saponins isolated from Pulsatilla koreana.
- To identify specific saponin structures responsible for anticancer effects.
- To compare the efficacy of these saponins with established chemotherapy drugs.
Main Methods:
- Isolation and characterization of seventeen saponins from Pulsatilla koreana root.
- In vitro cytotoxic activity assessment using the Sulforhodamine B (SRB) assay against human cancer cell lines (A-549, SK-OV-3, SK-MEL-2, HCT15).
- In vivo antitumor activity evaluation in BDF1 mice bearing Lewis lung carcinoma (LLC), comparing with Taxol and Doxorubicin.
Main Results:
- Saponins 5-17, featuring a free acidic functional group at C-28 of the aglycon, displayed moderate to significant cytotoxic activity.
- Saponins 1-4, esterified at C-28, showed no significant cytotoxic activity (ED50 > 300 microM).
- Oleanolic acid derivative (10) exhibited potent in vitro cytotoxicity (ED50 1.57-8.36 microM). Hederagenin derivatives (6 and 17) showed strong in vivo antitumor activity (IR 66.9% and 50.3%, respectively), outperforming Doxorubicin and Taxol.
Conclusions:
- The presence of a free acidic functional group at C-28 of the aglycon is crucial for cytotoxic activity.
- Specific hederagenin saponins with a defined sugar moiety (O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside at C-3) are potent antitumor agents.
- These findings highlight the potential of Pulsatilla koreana saponins as novel anticancer therapeutics.
