Kinetic Studies of the Photochemical Decomposition of Alkannin/Shikonin Enantiomers.

2005

Phytotherapy Research

Alkannin and shikonin (A[sol ]S) are pharmaceutical substances with a wide spectrum of biological properties. Radical scavenging activity is involved in aging processes, antiinssammatory, anticancer and wound healing activities. Hence, in the present study the DPPH radical scavenging activity of alkannin and shikonin, both monomeric and oligomeric, and extracts of Alkanna tinctoria roots were studied and a structure-activity relationship was approximated. It was shown that both monomeric and oligomeric alkannin and shikonin and also A[sol ]S esters exhibited extremely high radical scavenging activity. The presence of the naphthoquinone moiety seems to be essential for that activity, while the side chain of A[sol ]S possibly plays a minor role. Esterification of A[sol ]S on the side chain hydroxyl group does not affect radical scavenging activity. Organic solvents and olive oil (extracted at room temperature) extracts of Alkanna tinctoria roots, which contain as active ingredients A[sol ]S esters, exhibited very good antiradical activity. Alkannin and shikonin and their esters and also extracts of Alkanna tinctoria roots could be used promisingly in pharmaceutical and cosmetic preparations for their radical scavenging activity and probably for their antiaging activity.

Section: Introductionmentioning

confidence: 99%

Radical scavenging activity of Alkanna tinctoria root extracts and their main constituents, hydroxynaphthoquinones

2005

Phytotherapy Research

“…They are susceptible to several transformations, e.g. photochemical decomposition (Cheng et al, 1995;Chen et al, 1996), thermal degradation (Cho et al, 1999) and polymerization (Papageorgiou et al, 2002). Formation of dimeric and trimeric isohexenylnaphthazarins has also been observed during the fragmentation of the molecules in mass spectrometric analysis (Papageorgiou et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Study on isohexenylnaphthazarins polymerization in alkaline media

Biomedical Chromatography

2004

The chiral pair alkannin and shikonin (A/S) and their isohexenylnaphthazarin (IHN) esters, which are naturally occurring hydroxynaphthoquinones (HNQ), are potent pharmaceutical substances with a wide spectrum of biological activity. The stability of A/S and their derivatives during process and storage is crucial to their use as drugs, cosmetics and food additives. The influence of alkaline media and of IHN esters hydrolysis was experimentally investigated on IHN polymerization by size exclusion chromatography (SEC). It was proved that during IHN esters hydrolysis, polymeric A/S and IHN are formed. An optimization of the hydrolysis conditions of IHN esters was also approached in terms of polymerization. Hydrolysis of IHN from a pure mixture of pigments proved preferable to that of preliminary root extracts by means of IHN polymerization, even for analytical determination; non-polar solvents are proposed for the extraction of IHN from roots, followed by hydrolysis, aiming to minimize the polymeric IHN and A/S formed. It was also proved that polymerization of IHN in alkaline media and during hydrolysis of IHN esters proceeds through the intermediate formation of semiquinones; after acidification, coupling of semiquinones with phenoxyl radicals results in polymeric IHN structures.

“…The chirality of these substances has been shown to have little influence on the major biological activity of A/S. A/S and their derivatives are susceptible to several transformations, such as photochemical decomposition (Cheng et al, 1995;Chen et al, 1996), thermal degradation (Cho et al, 1999) and polymerization (Papageorgiou, 1976;Papageorgiou et al, 1998;Papageorgiou et al, 2002;Toribara and Underwood, 1949).…”

Section: Introductionmentioning

confidence: 99%

Study on polymerization of the pharmaceutical substances isohexenylnaphthazarins

Biomedical Chromatography

2003

Polymerization of naturally occurring isohexenylnaphthazarins (IHN), such as alkannin, shikonin (A/S) and their derivatives, which are potent pharmaceutical substances, significantly affects their use in pharmaceuticals, cosmetics and as food colorants, because it leads to reduction of the lustre of their red coloration, a decrease in their solubility and reduces the active monomeric IHN derivatives. In the present study, the influence of several crucial variables (processing and storage) was experimentally investigated on IHN polymerization by size exclusion chromatography (SEC). Temperature and solvent polarity increased significantly the concentration of hydroxynaphthoquinone (HNQ) polymers, while air and light exposure conditions did not significantly affect IHN polymerization. Low temperatures are proposed for all processes of industrial production of pharmaceutical preparations containing IHN and HNQ. An optimization of the industrial conditions used for the preparation of pharmaceutical and cosmetic preparations containing IHN, maximizing the active monomeric IHN fraction, was performed.