The phenylpropanoid glycoside verbascoside [2-(3,4-dihydroxyphenylethyl)-1-O-α-L-rhamnopyranosyl-(1→3)-β-D-(4-O-caffeyl)-glucopyranoside] (1) has been isolated as the main constituent of the crude extract of Buddleja brasiliensis Jacq. ex Spreng from Southern Brazil. The crude extract, main fractions and the compound 1 were evaluated for inhibition of the enzymes acetylcholinesterase (AChE), dipeptidyl peptidase-IV (DPP-IV) and prolyl oligopeptidase (POP). Compound 1 showed weak activity against DPP-IV with an IC(50) >> 150 µM and was inactive against AChE, with a pMIQ determined by bioautography of 9.6. In contrast, 1 displayed significant inhibition of POP in a dose-dependent manner with an IC(50) value of 1.3 ± 0.2 µM, similar to the positive control, baicalin, with a POP IC(50) of 12 ± 3 µM.

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A screening of the natural product chlorogenic acid, isolated from the Brazilian medicinal plant Hypericum brasiliense, caffeic acid, cinnamic acid, and p-methoxycinnamic acid, and derivatives of caffeoylquinic, caffeoyl, and cinnamoyl against the enzymes prolyl oligopeptidase and dipeptidyl peptidase IV was carried out. Caffeoylquinic, caffeoyl, and cinnamoyl derivatives were prepared using simple derivatization procedures and through coupling reactions with the amino acid proline. The dipeptidyl peptidase IV assay showed inhibitory activity of the tested compounds at a high concentration (500 µM) in the range of 81.5-7.2 %. In contrast, the derivatives methyl ester and 1,7-acetonide obtained from chlorogenic acid, and caffeic acid and its methyl ester derivative showed selectivity and activity as prolyl oligopeptidase inhibitors, with IC50 values of 3 to 14 mM.

In this work, four alkaloids from the stem bark of T. catharinensis were isolated, namely: voacangine (1); ethyl apovincaminate (2); affinisine (3) and voachalotine (4).The alkaloids were tested in vitro for antiproliferative capacity in eight tumor cell lines: U251 (glioma), MCF-7 (breast), NCI-ADR / RES (drug resistant ovary), 786-0 (kidney), NCI-H460 (lung), HT-29 (colon), K562 (leukemia) and PC-3 (prostate) and a non-tumor keratinocyte cell line (HaCat). Antiproliferative activity was observed after 48 hours and results expressed as the concentration needed to induce 50% growth inhibition (GI50) in µM. The chemotherapy drug Doxorubicin was used as a standard.The alkaloid affinisine (3) was the most promising, showing moderate inhibition rates in addition to the cytotoxic and cytocidal effect against all strains tested. It also proved to be a very promising compound, showing high selectivity rates when compared to the non-tumor keratinocyte cell line (HaCat).

Chlorogenic acid (1) and quercetin (4) were the main constituent responsible for the activity observed against POP. Parallel artificial membrane permeability assay of ethyl acetate fractions of both species showed that the metabolite that can effectively pass through the lipid membrane is 4, the aglycone form of 2, 3 and 5.