2 research outputs found
Synthesis and Antioxidant Activity of Hydroxytyrosol Alkyl-Carbonate Derivatives
Three procedures have been investigated
for the isolation of tyrosol (<b>1</b>) and hydroxytyrosol (<b>2</b>) from a phenolic extract obtained from the solid residue
of olive milling. These three methods, which facilitated the recovery
of these phenols, were chemical or enzymatic acetylation, benzylation,
and carbomethoxylation, and subsequent carbonylation or acetonation
reactions. Several new lipophilic alkyl-carbonate derivatives of hydroxytyrosol
have been synthesized, coupling the primary hydroxy group of this
phenol, through a carbonate linker, using alcohols with different
chain lengths. The antioxidant properties of these lipophilic derivatives
have been evaluated by different methods and compared with free hydroxytyrosol
(<b>2</b>) and also with the well-known antioxidants BHT and
α-tocopherol. Three methods were used for the determination
of this antioxidant activity: FRAP and ABTS assays, to test the antioxidant
power in hydrophilic media, and the Rancimat test, to evaluate the
antioxidant capacity in a lipophilic matrix. These new alkyl-carbonate
derivatives of hydroxytyrosol enhanced the antioxidant activity of
this natural phenol, with their antioxidant properties also being
higher than those of the commercial antioxidants BHT and α-tocopherol.
There was no clear influence of the side-chain length on the antioxidant
properties of the alkyl-carbonate derivatives of <b>2</b>, although
the best results were achieved mainly by the compounds with a longer
chain on the primary hydroxy group of this natural phenolic substance
Solid-Phase Library Synthesis of Bi-Functional Derivatives of Oleanolic and Maslinic Acids and Their Cytotoxicity on Three Cancer Cell Lines
A wide
set of 264 compounds has been semisynthesized with high
yields and purities. These compounds have been obtained through easy
synthetic processes based on a solid-phase combinatorial methodology.
All the members of this library have one central core of a natural
pentacyclic triterpene (oleanolic or maslinic acid) and differ by
6 amino acids, coupled with the carboxyl group at C-28 of the triterpenoid
skeleton, and by 10 different acyl groups attached to the hydroxyl
groups of the A-ring of these molecules. According to the literature
on the outstanding and promising pharmacological activities of other
similar terpene derivatives, some of these compounds have been tested
for their cytotoxic effects on the proliferation of three cancer cell
lines: B16–F10, HT29, and Hep G2. In general, we have found
that around 70% of the compounds tested show cytotoxicity in all three
of the cell lines selected; around 60% of the cytotoxic compounds
are more effective than their corresponding precursors, that is, oleanolic
(OA) or maslinic (MA) acids; and nearly 50% of the cytotoxic derivatives
have IC<sub>50</sub> values between 2- to 320-fold lower than their
corresponding precursor (OA or MA)