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Abstract Thousands of coumarin compounds have been isolated an d ident if ied in di fferent plant species. These compounds play an important role in ant icancer drug development due to thei r wide range of biological act ivi t ies and their ef fect against di fferent types of cancer cel ls. Therefore, this study was car ried out to gain informat ion about the mechanism of these compounds and searching for novel cytotoxic agents. Seven plants containing coumarin derivat ives and ten new furocoumarin analogues were used in this work. HepG-2 cel ls (l iver cancer cel l l ine) were treated wi th concent rat ions ranged f rom 0.1 - 1 0 0 0 μ g /ml f o r 7 2 hours. Compound number 9 showed highest reduct ion in cel l viabi l i ty percentage, and exhibi ted the highest inhibi tory act ivi ty wi th IC50 ( inhibi tory concent rat ion for 50% of cel ls) equal 11.97 μ g/ml , a n d f al l wi t h i n t h e Ame r i ca n Na t i o n al Cancer Inst i tute cr i teria; whi le the other compounds recorded medium or weak ef fect as compared wi th the standard drug Doxorubicin (IC50=0.87 μ g /ml ) . The plant extracts also reduced the viabi l i ty of cancer cel ls in a dose dependent manner . Their cytotoxic ef fect was more observed at the higher concentrat ions. IC50 of the seven plant extracts was ranged f rom 121.4 μg/ml for Verbascum thapsus to 511.8 μg/ml for Ammi majus. Root t ip cel ls of Pisum sat ivum plant were t reated wi th concent rat ions ranged f rom 0.05–1.0 mg/ml of compounds number 9 and 8 and wi th 2.19 – 35 mg/ml for the natural plant extracts of Achi l lea mi l lefol ium and Verbascum thapsus . Resul ts showed signi ficant decrease in mi tot ic index that increased gradual ly by increasing the concent rat ion and the t ime of treatments; in addi t ion to di fferent types of mi tot ic abnormal i t ies were recorded such as st ickiness and chromosome breakage. The expression level of two cel l cycle regulatory genes; cycl in B1 and cycl in D1 were examined using RT-PCR techniques. The resul ts indicated that cycl in B1 was down regulated in response to t reatment of Pisum sat ivum roots wi th the concent rat ions 0.5 mg/ml of compound 9 and 1.0 mg/ml of compound 8, and wi th 17.5, 35 mg/ml of the ext racts of Verbascum thapsus and Achi l lea mi l lefol ium as compared wi th the reference gene β- tubul in-3. Moreover, only compound number 9 caused decrease in cycl in D1 in response to treatment wi th 0.5 mg/ml , as compared wi th compound number 8; ext racts of Verbascum thapsus and Achi l lea mi l lefol ium which showed no effect , indicat ing the effect of compound number 9 on the cel l cycle ar rest at the t ransi t ion point G1 /S. The genomic stabi l i ty percentage in Pisum sat ivum plant cel ls t reated wi th the previous materials using ISSR-DNA fingerprints showed change in band number and decrease in genomic template stabi l i ty (GTS) values in al l treatments. Compound number 9 recorded the lowest GTS (46%) whi le compound number 8 recorded 64% in comparison to the untreated cont rol , indicat ing that compound 9 is more ef fect ive on genome stabi l i ty. The GTS value of plant ext racts decreased wi th increasing the concent rat ions. The lowest GTS (76.12%) recorded wi th the highest concent rat ion (35 mg/ml) of Verbascum thapsus; whi le recorded 88.06% in samples treated wi th the same concent rat ion of Achi l lea mi l lefol ium. Thus, 0.5 mg/ml of compound 9 have g r ea t e r d ama g e o n c el l ’ s g en et i c mat er i al i n d i c at i v e o f t h e genotoxici ty at this concentrat ion. On the other hand, the molecular docking technique showed that this compound has a good abi l i ty to inhibi t topoisomerase I which in turn wi l l lead to cancer cel l inhibi t ion through the inhibi t ion of DNA repl icat ion. |