Terpenoids. XXII.1 Triterpenes from Some Mexican and South American Plants2

Bifunctionalized Betulinic Acid Conjugates with C-3-Monodesmoside and C-28-Triphenylphosphonium Moieties with Increased Cancer Cell Targetability

A convenient synthesis is presented for a new class of bioactive bifunctionalized conjugates of lupane-type triterpenoids with triphenylphosphonium (TPP) and glycopyranosyl targeting moieties. The main synthesis steps include glycosylation of haloalkyl esters of the triterpene acid at the C-3 position by the imidate derivatives of glycopyranose followed by the product modification at the C-28 position with triphenylphosphine. The conjugates of betulinic acid (BetA) with TPP and d-glucose, l-rhamnose, or d-mannose moieties were thus synthesized as potential next-generation BetA-derived anticancer compounds. LC-MS/MS analysis in glucose-free physiological solution indicated that the glycosides showed better accumulation in PC-3 prostate cancer cells than both BetA and TPP-BetA conjugate, while the transporting effect of monosaccharide residues increased as follows: d-mannose < l-rhamnose ≈ d-glucose. At saturated concentrations, the glycosides caused a disturbing effect on mitochondria with a more drastic drop in transmembrane potential but weaker overproduction of mitochondrial reactive oxygen species (ROS) compared to TPP-BetA conjugate. Cytotoxicity of the glycosides in culture medium was comparable with or higher than that of the nonglycosylated conjugate, depending on the cancer cell line, whereas the compounds were less active toward primary fibroblasts. Glycosylation tended to increase pro-apoptotic and decrease pro-autophagic activities of the BetA derivatives. Cytotoxicity of the synthesized glycosides was considered in comparison with the summarized data on the natural and modified BetA glycosides. The results obtained are important for the development of bifunctionalized conjugates of triterpenoids with an increased cancer cell targetability.

Chemistry, Biological Activities and In Silico Bioprospection of Sterols and Triterpenes from Mexican Columnar Cactaceae

The Cactaceae family is an important source of triterpenes and sterols. The wide uses of those plants include food, gathering, medicinal, and live fences. Several studies have led to the isolation and characterization of many bioactive compounds. This review is focused on the chemistry and biological properties of sterols and triterpenes isolated mainly from some species with columnar and arborescent growth forms of Mexican Cactaceae. Regarding the biological properties of those compounds, apart from a few cases, their molecular mechanisms displayed are not still fully understand. To contribute to the above, computational chemistry tools have given a boost to traditional methods used in natural products research, allowing a more comprehensive exploration of chemistry and biological activities of isolated compounds and extracts. From this information an in silico bioprospection was carried out. The results suggest that sterols and triterpenoids present in Cactaceae have interesting substitution patterns that allow them to interact with some bio targets related to inflammation, metabolic diseases, and neurodegenerative processes. Thus, they should be considered as attractive leads for the development of drugs for the management of chronic degenerative diseases.

An Improved Scalable Synthesis of α- and β-Amyrin

The synthesis of α- and β-amyrin was accomplished starting from easily accessible starting materials, oleanolic, and ursolic acid. The procedures allow the preparation of β-amyrin in an exceptionally short scalable manner via selective iodation and reduction. For α-amyrin, a different synthetic approach had to be chosen providing access to α-amyrin in medium-to-large scale.

Pharmacological and chemical screening of Byrsonima crassifolia, a medicinal tree from Mexico. Part I

Leaf and bark extracts of Byrsonima crassifolia displayed concentration-dependent, spasmogenic effects on rat fundus in vitro and biphasic effects on rat jejunum and ileum in vitro. Dose-related in vivo effects in intact rats using hippocratic screening were: decrease in motor activity, mild analgesia, back tonus, enophthalmos, reversible palpebral ptosis, ear blanching, Robichaud positive, catalepsy (awake) and strong hypothermia. Rat fundus in vitro was used as the bioassay to carry out an activity-directed separation. Bioactive material was concentrated in a 2% acetic acid leaf extract (HOAcE). Potency of HOAcE was increased by the presence of pargyline in the bathing solution. HOAcE was antagonized noncompetively by 1(1-naphthyl) piperazine (1-NP) and cyproheptadine and antagonized competitively by atropine (ATR). Cumulative concentration-response curves of HOAcE and serotonin (5-HT) did not show significant departure from parallelism (P > 0.1) and 5-HT potency was 6040 times that of HOAcE (95% confidence limits: 4620-7850). Solvent extraction of HOAcE split the spasmogenic activity of HOAcE into two types: (i) high-efficacy, low-potency, n-butanol-extracted, pargyline- and 1-NP-sensitive, ATR-insensitive activity, and (ii) low-efficacy, high-potency, ethyl acetate-extracted, pargyline-insensitive, ATR- and 1-NP-sensitive activity. HOAcE lacked muscarinic and nicotinic effects on rat jejunum and frog rectus abdominis. Results suggest the presence of more than one spasmogenic compound in the plant.

Pharmacological screening of some Brazilian plants

Forty-five species of plants from several botanical families growing in North East Brazil have been examined for toxicity on mice and small fishes, cat blood pressure and respiration, isolated toad heart and rectus abdominis muscle, guinea-pig ileum, rabbit duodenum and rat uterus. A high toxicity to mice and fishes was exhibited by aqueous (A) and ethanolic (B) extracts from Luffa operculata, Peschiera affinis, Pithecelobium multiflorum (gall) and Zizyphus joazeiro and by extract B from Pithecelobium multiflorum (stembark). Cardiorespiratory activity was shown by Annona squamosa, Byrsonima sericea, Crataeva tapia, Erythrina velutina, Fagara rhoifolia, Operculina macrocarpa, Perschiera affinis, Pithecelobium multiflorum, Spondias lutea and Zizyphus joazeiro. Extracts A and B from Operculina macrocarpa and Pithecelobium multiflorum, extract A from Luffa operculata and Zizyphus joazeiro and extract B from Crataeva tapia and Peschiera affinis promoted a contraction of the toad rectus abdominis muscle. Both extracts from Annona aquamosa and Fagara rhoifolia (leaf) provoked a spasmogenic effect on guineapig ileum and a spasmolytic one on rabbit duodenum. Extracts A and B from Pithecelobium multiflorum, Vitex gardneriana and Zizyphus joazeiro exhibited a spasmogenic activity on both preparations, while extracts A and B from Peschiera affinis and extract B from Erythrina velutina also evidenced a spasmolytic activity on both preparations. Oxytocic activity was shown by both extracts from Annona squamosa, Byrsonima sericea, Pithecelobium multiflorum and Vitex gardneriana.