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Several PEGylated derivatives of oleanolic and maslinic acids have been semi-synthesized, attaching one acid-PEG reagent to the hydroxyl group/s at C-2 or C-2/C-3 of the A rings of these natural triterpenes, and also to their corresponding C-28 benzyl derivatives. Several monomeric and dimeric PEGylated compounds have also been produced by linking one diamine-PEG reagent to the carboxyl group at C-28 of the same natural triterpenes and also to their corresponding C-2 or C-2/C-3 acetylated derivatives. The cytotoxic effects of 12 triterpenic PEGylated derivatives in three cancer-cell lines (B16 F10, HT29, and Hep G2) have been assayed. The best results have been achieved by the PEGylated-amine derivative of oleanolic acid, with IC 50 concentrations between 0.22 and 3.78 μM, being between 28- and 963-fold more effective than its natural precursor. The percentages of apoptosis induction have also been determined for the five PEGylated derivatives with the lowest cytotoxicity data. All five compounds showed apoptotic effects on the treated cells, with a total apoptosis rate of 99% in the B16 F10 cells, 80% in the Hep G2 cells, and 51% in the HT29 cells. We have also studied the changes in the mitochondrial membrane potential (MMP) to elucidate the possible mechanism involved in the apoptotic responses (intrinsic or extrinsic). Finally, to verify the results found in the cytometry assays, we have used fluorescence microscopy techniques to determine changes in the cell morphology. These PEGylated derivatives of natural triterpenoids, which can induce apoptosis at very low concentrations in different tumour lines, may represent new effective therapeutic drugs against these diseases. [ABSTRACT FROM AUTHOR]

The pentacyclic triterpenoids methyl oleanolate, methyl maslinate, methyl 3β-hydroxyolean-9(11),12-dien-28-oate, and methyl 2α,3β-dihydroxy-12β,13β-epoxyolean-28-oate were biotransformed by Rhizomucor miehei CECT 2749. Microbial transformation of methyl oleanolate produced only a 7β,30-dihydroxylated metabolite with a conjugated 9(11),12-diene system in the C ring. Biotransformation of the substrate with this 9(11),12-diene system gave the same 7β,30-dihydroxylated compound together with a 7β,15α,30-trihydroxyl derivative. The action of this fungus ( R. miehei ) on methyl maslinate was more varied, isolating metabolites with a 30-hydroxyl group, a 9(11),12-diene system, an 11-oxo group, or an 12-oxo group. Microbial transformation of the substrate with a 12β,13β-epoxy function resulted in the isolation of two metabolites with 12-oxo and 28,13β-olide groups, hydroxylated or not at C-7β, together with a 30-hydroxy-12-oxo derivative. The structures of these derivatives were deduced by extensive and rigorous spectroscopic studies. [ABSTRACT FROM AUTHOR]

Abstract: A broad set of potential bioactive conjugate compounds has been semi-synthesized through solution- and solid-phase organic procedures, coupling two natural pentacyclic triterpene acids, oleanolic (OA) and maslinic acids (MA), at the hydroxyl groups of the A-ring of the triterpene skeleton, with 10 different acyl groups. These acyl OA and MA derivatives have been tested for their anti-proliferative (against the b16f10 murine melanoma cancer cells) and antiviral (as inhibitors of the HIV-1-protease) effects. Several derivatives have shown high levels of early and total apoptosis (up to 90%). Most of the compounds that exhibited anti-proliferative effects also generated ROS, probably involving the activation of an intrinsic apoptotic route. The only four compounds that did not cause the release of ROS could be related to the participation of a probable extrinsic activation of the apoptosis mechanism. A great number of these acyl OA and MA derivatives have proved to be potent inhibitors of the HIV-1-protease, the most active inhibitors having IC50 values between 0.31 and 15.6 μM, these values being between 4 and 186 times lower than their non-acylated precursors. The potent activities exhibited in the apoptosis-activation processes and in the inhibition of the HIV-1-protease by some OA and MA acylated derivatives imply that these compounds could be used as new, safe, and effective anticancer and/or antiviral drugs. [Copyright &y& Elsevier]

Highlights: [•] Rhizomucor miehei inserted hydroxyl groups at non-activated positions of the substrates. [•] The microorganism showed oxidation reactions of a hydroxyl group and the double bond of the triterpenic acids. [•] The structure of metabolites with a lactone group was corroborated by chemical correlation. [•] Queretaroic acid, one of the isolated metabolites, presents remarkable biological properties. [Copyright &y& Elsevier]

Abstract: Maslinic acid (2α,3β-dihydroxyolean-12-en-28-oic acid), a natural dihydroxylated pentacyclic triterpene acid isolated from olive-pressing residues, has been investigated together with some of its derivatives regarding the induction of apoptosis in B16F10 melanoma cells. Some of the compounds tested are described in this work, but others come from previous studies. Ten of these derivatives induce over 80% of apoptosis, clearly promoting cell death in B16F10 melanoma. By contrast, the induction cell death through necrosis was very slightly significant with these compounds. These results indicate that maslinic acid derivatives are promising chemopreventive and chemotherapeutic agents. [Copyright &y& Elsevier]

Abstract: Maslinic acid (1) has been coupled at C-28 with several α- and ω-amino acids by using solution- and solid-phase synthetic procedures. Twelve derivatives (2–13) with a single amino acid residue were prepared in solution phase, whereas a dipeptide (14), a tripeptide (15), and a series of conjugate dipeptides (16–24) were synthesized in solid phase. The anti-HIV activity of these compounds was assessed on MT-2 cells infected with viral clones carrying the luciferase gene as a reporter. While in maslinic acid (1) were present both cytotoxic and antiviral activities, only the derivatives 13 and 24 showed anti-HIV-1 activity and therefore represent a novel class of anti-HIV-1 compounds. [Copyright &y& Elsevier]