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The collateral sensitivity effect is among the most promising strategies for overcoming multidrug resistance in cancer. In this work, 28 cucurbitane-type triterpenoids (1: -28: ), previously isolated from the African medicinal plant Momordica balsamina and its derivatives, were evaluated for their collateral sensitivity effect on three different human cancer entities, gastric (EPG85-257), pancreatic (EPP85-181), and colon (HT-29), each with two different multidrug-resistant variants. One was selected for its resistance to daunorubicin (EPG85-257RDB, EPP85-181RDB, HT-29RDB) and the other was selected for its resistance to mitoxantrone (EPG85-257RNOV, EPP85-181RNOV, HT-29RNOV). On gastric cell lines, the best results were obtained for compounds 3: and 10: , which exhibited a collateral sensitivity effect together with high antiproliferative activity. In turn, on colon cancer cell lines, the best multidrug resistance-selective antiproliferative effects were observed for derivatives 11, 13: , and 15: , which showed collateral sensitivity effects against both resistant variants. Compounds 11: and 3: were also the most selective against the multidrug resistance pancreatic cells lines. Some compounds, such 6, 10, 11: and 15: , were previously found to be strong P-glycoprotein modulators, thus highlighting their potential as promising leads for overcoming multidrug resistance in cancer cells., Competing Interests: The authors declare no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Four new diterpenes were isolated from the methanolic extract of Euphorbia piscatoria, two ent-abietanes (1, 2) and two lathyrane-type macrocyclic diterpenes (3, 4), along with three known diterpenes (5-7). Their structures were characterized by spectroscopic methods, mainly 1D and 2D NMR ((1)H, (13)C, DEPT, COSY, HMBC, HMQC, and NOESY) experiments. Compound 2, with an unusual structure, might be considered intermediate in the biosynthesis of ent-abietane α,β-unsaturated lactones, commonly found in Euphorbia species. Therefore, a possible biogenetic pathway is proposed. The MDR reversal potential of macrocyclic diterpenes 3-5 was evaluated through a drug combination assay, using the L5178Y mouse T lymphoma cell line transfected with the human MDR1 gene. Compounds 3-5 were able to enhance, synergistically, the antiproliferative activity of doxorubicin (combination indexes < 0.5). Moreover, compounds 1-6 were also assessed for their antiproliferative activity on human MDR cancer cell models, namely gastric, pancreatic, and colon. Weak antiproliferative activity was observed for compounds 1 (IC50 = 66.02 ± 7.10 µM) and 4 (IC50 = 39.51 ± 3.82 µM) on the MDR gastric cell line., (Georg Thieme Verlag KG Stuttgart · New York.)

Twelve phenolic compounds, including three stilbenes, two flavonoids, two coumarins, one neolignan, and four lignans, isolated from Euphorbia and Pycnanthus species or obtained by derivatization, were assayed for their potential antineoplastic efficacy in three human cancer cell lines: gastric (EPG85-257), pancreatic (EPP85-181), and colon (HT-29) carcinomas as well as derived multidrug-resistant sublines. In each case, two different multidrug-resistant variants, i.e., cell lines with classical and atypical MDR phenotype, were used. The majority of the MDR cancer sublines showed increased sensitivities to the studied compounds when compared to the parental sublines. The most active compound was the flavonoid naringenin, found to be 15-fold more effective against the atypical MDR subline of gastric carcinoma than in parental drug-sensitive cells. Furthermore, the stilbene trans-3,5,3',4'-tetramethoxypiceatannol and the lignans 4'-hydroxy-3,3',4-trimethoxylignan and heliobuphthalmin also exhibited high antineoplasic activities against the classical MDR subline derived from gastric carcinoma. The results of this study suggest that some phenolic compounds might be valuable for the treatment of multidrug-resistant cancer cells., (Georg Thieme Verlag KG Stuttgart.New York.)

Three new jatrophane diterpene polyesters named tuckeyanols A and B and euphotuckeyanol, as well as ten known compounds, helioscopinolides A, B, D and E, naringenin, aromadendrin, coniferaldehyde, 4,20-dideoxy-5-hydroxyphorbol 12,13-diisobutyrate, 4,20-dideoxy-5-hydroxyphorbol 12-benzoate-13-isobutyrate and dehydrodiconiferyl diacetate, were isolated from the methanolic extract of Euphorbia tuckeyana. Their structures were elucidated by physical and spectroscopic methods including 1 D and 2 D homo- and heteronuclear NMR techniques (COSY, HMQC, HMBC and NOESY), and HR-mass spectrometry. Four of the isolated compounds were investigated for their antiproliferative activity in three human gastrointestinal cancer cell lines: gastric (EPG85-257), pancreatic (EPP85-181) and colon (HT-29) carcinomas. Three of them have showed to be moderate inhibitors of the growth of gastric and pancreatic tumor cell lines.