Quince is a shrub or small tree of the rose family. The common quince Cydonia oblonga is a tree with edible fruits cultivated from ancient times in Asia and in the Mediterranean area. The quince fruit is similar to that of the related apple and pear but is astringent, and hence it is used chiefly cooked in preserves. Marmalade is said to have first been made from quince. Quince jam is quite tasty and is a fine addition to more commonly eaten jams.

Antioxidant properties
Evaluation of free radical scavenging and antihemolytic activities of quince (Cydonia oblonga) leaf: a comparative study with green tea (Camellia sinensis).
Food Chem Toxicol. 2009. Costa RM, Magalhães AS, Pereira JA, Andrade PB, Valentão P, Carvalho M, Silva BM. CEBIMED, Faculdade de Ciências da Saúde, Universidade Fernando Pessoa, R. Carlos da Maia, 296, 4200-150 Porto, Portugal.
This study aimed to determine the phenolic profile and to investigate the antioxidant potential of quince (Cydonia oblonga) leaf, comparing it with green tea (Camellia sinensis). For these purposes, methanolic extracts were prepared and phenolics content of quince leaf was determined by HPLC/UV. The antioxidant properties were assessed. 5-O-Caffeoylquinic acid was found to be the major phenolic compound in quince leaf extract. Cydonia oblonga leaf exhibited a significantly higher reducing power than green tea. Quince leaf extracts showed similar DPPH radical scavenging activities but significantly higher than those presented by green tea. Under the oxidative action of AAPH, quince leaf methanolic extract significantly protected the erythrocyte membrane from hemolysis in a similar manner to that found for green tea. These results point that quince leaf may have application as preventive or therapeutic agent in diseases in which free radicals are involved.

Diabetes and blood sugar
Iran J Pharm Res. 2015. Hypolipidemic, Hepatoprotective and Renoprotective Effects of Cydonia Oblonga Mill. Fruit in Streptozotocin-Induced Diabetic Rats. The present study indicates that aqueous extract of quince Mill. Is able to improve some of the symptoms associated with diabetes and possesses hypolipidemic, hepatoprotective, and renoprotective effects in streptozotocin-induced diabetic rats.

J Ethnopharmacol. 2014. Effect of Cydonia oblonga fruit and leaf extracts on blood pressure and blood rheology in renal hypertensive rats. fCOM extracts have antihypertensive activity in renal hypertensive rats. The additional effect on rheology, compared to captopril, may convey added interest. Further studies of these effects in man appear warranted.

Quince Research studies
Natural wax constituents of a supercritical fluid CO(2) extract from quince Cydonia oblonga Mill pomace.
Anal Bioanal Chem. 2008. Lorenz P, Berger M, Bertrams J, Wende K, Wenzel K, Lindequist U, Meyer U, Stintzing FC. WALA Heilmittel GmbH, Dorfstrasse 3, 73087, Bad Boll/Eckwälden, Germany.
The chemical constituents of a lipophilic extract from quince, obtained by supercritical fluid CO(2) extraction of the dried fruit pomace were investigated. Solvent partition of Cydonia oblonga wax with n-hexane or acetone yielded an insoluble (crystalline) and a soluble (oily) fraction. Both fractions were analyzed separately. The insoluble fraction consisted of saturated n-aldehydes, n-alcohols and free n-alkanoic acids of carbon chain lengths between 22 and 32, with carbon chain lengths of 26 and 28 dominating. Triterpenoic acids were separated from the hexane-insoluble matter and identified as a mixture of ursolic, oleanolic and betulinic acids. The major constituents of the hexane-soluble fraction were glycerides of linoleicand oleic acids, accompanied by free linoleic, oleic and palmitic acids. Moreover beta-sitosterol, Delta(5)-avenasterol as well as trace amounts of other sterols were found. Finally the carotenoids phytoene and phytofluene were identified, yielding 1.0 and 0.3% of the quince wax, respectively.

Quince (Cydonia oblonga miller) fruit characterization using principal component analysis.
J Agric Food Chem. 2005.
Faculdade de Farmacia, Universidade do Porto, R. Anibal Cunha, Portugal.
This paper presents a large amount of data on the composition of quince fruit with regard to phenolic compounds, organic acids, and free amino acids. Subsequently, principal component analysis (PCA) is carried out to characterize this fruit. The main purposes of this study were (i) the clarification of the interactions among three factors-quince fruit part, geographical origin of the fruits, and harvesting year-and the phenolic, organic acid, and free amino acid profiles; (ii) the classification of the possible differences; and (iii) the possible correlation among the contents of phenolics, organic acids, and free amino acids in quince fruit. With these aims, quince pulp and peel from nine geographical origins of Portugal, harvested in three consecutive years, for a total of 48 samples, were studied. PCA was performed to assess the relationship among the different components of quince fruit phenolics, organic acids, and free amino acids. Phenolics determination was the most interesting. The difference between pulp and peel phenolic profiles was more apparent during PCA. Two PCs accounted for 81.29% of the total variability, PC1 (74%) and PC2 (7%). PC1 described the difference between the contents of caffeoylquinic acids (3-O-, 4-O-, and 5-O-caffeoylquinic acids and 3,5-O-dicaffeoylquinic acid) and flavonoids (quercetin 3-galactoside, rutin, kaempferol glycoside, kaempferol 3-glucoside, kaempferol 3-rutinoside, quercetin glycosides acylated with p-coumaric acid, and kaempferol glycosides acylated with p-coumaric acid). PC2 related the content of 4-O-caffeoylquinic acid with the contents of 5-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acids. PCA of phenolic compounds enables a clear distinction between the two parts of the fruit. The data presented herein may serve as a database for the detection of adulteration in quince derivatives. quince fruit quince tree flowering quince.