Guava leaves polyphenolics-rich extract inhibits vital enzymes implicated in gout and hypertension in vitro.
OBJECTIVE
Elevated uric acid level, an index of gout resulting from the over-activity of xanthine oxidase (XO), increases the risk of developing hypertension. However, research has shown that plant-derived inhibitors of XO and angiotensin 1-converting enzyme (ACE), two enzymes implicated in gout and hypertension, respectively, can prevent or ameliorate both diseases, without noticeable side effects. Hence, this study characterized the polyphenolics composition of guava leaves extract and evaluated its inhibitory effect on XO and ACE in vitro.


METHODS
The polyphenolics (flavonoids and phenolic acids) were characterized using high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD). The XO, ACE, and Fe(2+)-induced lipid peroxidation inhibitory activities, and free radicals (2,2-diphenylpicrylhydrazyl [DPPH]* and 2,2´-azino-bis-3-ethylbenzthiazoline-6-sulphonic [ABTS]*(+)) scavenging activities of the extract were determined using spectrophotometric methods.


RESULTS
Flavonoids were present in the extract in the order of quercetin > kaempferol > catechin > quercitrin > rutin > luteolin > epicatechin; while phenolic acids were in the order of caffeic acid > chlorogenic acid > gallic acids. The extract effectively inhibited XO, ACE and Fe(2+)-induced lipid peroxidation in a dose-dependent manner; having half-maximal inhibitory concentrations (IC50) of 38.24 ± 2.32 μg/mL, 21.06 ± 2.04 μg/mL and 27.52 ± 1.72 μg/mL against XO, ACE and Fe(2+)-induced lipid peroxidation, respectively. The extract also strongly scavenged DPPH* and ABTS*(+).


CONCLUSIONS
Guava leaves extract could serve as functional food for managing gout and hypertension and attenuating the oxidative stress associated with both diseases.
Department of Biosciences and Biotechnology, Biochemistry Unit, Kwara State University, Malete, P.M.B., 1530, Ilorin, Nigeria.
Emmanuel Anyachukwu
EA
Irondi
Department of Veterinary Physiology, Biochemistry and Pharmacology, University of Ibadan, Nigeria.
Samson Olalekan
SO
Agboola
Department of Biochemistry, Functional Foods and Nutraceuticals Unit, Federal University of Technology, Akure, Nigeria P.M.B., 704, Akure 340001, Nigeria.
Ganiyu
G
Oboh
Department of Industrial Pharmacy, Phytochemical Research Laboratory, Federal University of Santa Maria, Building 26, room 1115, Santa Maria, CEP 97105-900, Brazil.
Aline Augusti
AA
Boligon
Department of Industrial Pharmacy, Phytochemical Research Laboratory, Federal University of Santa Maria, Building 26, room 1115, Santa Maria, CEP 97105-900, Brazil.
Margareth Linde
ML
Athayde
Department of Chemistry, Cape Peninsula University of Technology, Cape Town, South Africa.
Francis O
FO
Shode
Angiotensin I-converting enzyme; Fe2+-induced lipid peroxidation; oxidative stress; xanthine oxidase