Abstract
Background: Oleanolic acid is a natural plant adaptogen, and tryptamine is a natural psychoactive drug. To compare their effects of with the effect of their derivatives, tryptamine and fluorotryptamine amides of oleanolic acid were designed and synthesized. Methods: The target amides were investigated for their pharmacological effect, and basic supramolecular self-assembly characteristics. Four human cancer cell lines were involved in the screening tests performed by standard methods. Results: The ability to display cytotoxicity and to cause selective cell apoptosis in human cervical carcinoma and in human malignant melanoma was seen with the three most active compounds of the prepared series of compounds. Tryptamine amide of (3β)-3-(acetyloxy)olean-12-en-28-oic acid (3a) exhibited cytotoxicity in HeLa cancer cell lines (IC50 = 8.7 ± 0.4 µM) and in G-361 cancer cell lines (IC50 = 9.0 ± 0.4 µM). Fluorotryptamine amides of (3β)-3-(acetyloxy)olean-12-en-28-oic acid (compounds 3b and 3c) showed cytotoxicity in the HeLa cancer cell line (IC50 = 6.7 ± 0.4 µM and 12.2 ± 4.7 µM, respectively). The fluorotryptamine amide of oleanolic acid (compound 4c) displayed cytotoxicity in the MCF7 cancer cell line (IC50 = 13.5 ± 3.3 µM). Based on the preliminary UV spectra measured in methanol/water mixtures, the compounds 3a–3c were also found to self-assemble into supramolecular systems. Conclusions: An effect of the fluorine atom present in the molecules on self-assembly was observed with 3b. Enhanced cytotoxicity has been achieved in 3a–4c in comparison with the effect of the parent oleanolic acid (1) and tryptamine. The compounds 3a–3c showed a strong induction of apoptosis in HeLa and G-361 cells after 24 h.
Highlights
Oleanolic acid ((3β)-3-hydroxyolean-12-en-28-oic acid (1), Scheme 1) is a pentacyclic triterpenoid acid bearing a 6-6-6-6-6 skeleton of the oleanane type
The most active compounds3a–3c identified in this screening were evaluated for induction of apoptosis in cancer cells
They showed a strong induction of apoptosis in cervical carcinoma and malignant melanoma cells after 24 h
Summary
Oleanolic acid ((3β)-3-hydroxyolean-12-en-28-oic acid (1), Scheme 1) is a pentacyclic triterpenoid acid bearing a 6-6-6-6-6 skeleton of the oleanane type. Oleanolic acid (1), despite its low bioavailability, displays a broad spectrum of pharmacological activity, and it is considered to be an adaptogen [4] It has a protective effect on the human liver, where it acts against serious liver injuries and against hepatitis [1], and it displays antitumor activity [5]. Application of fluorine atom or trifluoromethyl group as structural modifiers of biologically active compounds has appeared since 1970s [24]. Several review papers have been published in pentacyclic triterpenoids aonf 1d5 their structural modifications, including those resulting in the investigation of novel nitrogen-containing compounds [28,29,30,31,32]. TToo bbeeggiinn ddeessiiggnniinngg tthhee ttaarrggeett ccoommppoouunnddss,,wweettooookkiinnttooaaccccoouunntttthheekknnoowwnnlloowwssooll-uubbiilliittyy ooff 11 iinn wwaatteerr,, aanndd,, tthheerreeffoorree,, iittss llooww bbiiooaavvaaiillaabbiilliittyy. Purification of the crude products by column chromatography gave compounds 4a–4c in >90% yields
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