Background: Free radicals are involved in various human diseases that can possibly be prevented by antioxidants. There are many but rather expensive methods to determine total antioxidant capacity of human plasma (for endogenous antioxidant levels) or plant extracts/natural compounds (for antioxidant potential in terms of radical inhibiting or scavenging properties). We describe a simple, fast and economical 'crocin assay' using the Indian spice saffron.
Methods: In crocin assay, the extent of bleaching of crocin, a carotenoid from saffron, by peroxyl radicals generated by thermal decomposition of azo-initiator was measured. We examined its applicability to clinical samples and plant extracts.
Results: The cost of Indian saffron is almost 38 times less per unit dry weight compared to the 'Sigma' saffron. Yet, it gives 26 times better yield of crocin than that from 'Sigma' saffron. It was also shown that Indian saffron is rich in crocin. The total antioxidant capacity (TAC) values of human plasma from normal, healthy individuals, using Sigma as well as Indian crocin, expressed in terms of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) equivalent antioxidant capacity (TEAC), were comparable. We have also demonstrated that crocin assay can be used for clinical samples such as plasmas from healthy and diabetic individuals. The antioxidant potentials, TEAC, of plant extracts and pure natural compounds by Indian and Sigma crocin assays were similar. Addition of uric acid to plasma induced a concentration-dependent response. The assay was compared to standard radical scavenging 1,1'-diphenyl-2-picrylhydrazyl (DPPH) assay and was found to match well, showing better sensitivity and hence validates this assay for natural compounds and clinical samples.
Conclusions: Development of crocin assay using the Indian saffron is economical and sensitive method for measurement of total antioxidant capacities from human plasma as well as natural compounds and plant extracts.