Quality assessment of marketed food supplements and herbal tea products of olive leaf in Turkey

Abstract

In this study, qualitative and quantitative analysis of commercially available food supplements composed of olive leaf extract and herbal tea products containing olive leaf were evaluated by High-Performance Thin-Layer Chromatography (HPTLC) and a newly developed and validated High-Performance Liquid Chromatographic (HPLC) method for their quality assessment. In addition, leaves of two varieties of Olea europaea L. (var. europaea and var. sylvestris) grown in Turkey which were assigned as reference plant materials and their chemical compositions were also comparatively analyzed by HPTLC. Then HPTLC fingerprints of reference plant materials were compared to the marketed olive leaf samples. For quantification of oleuropein and luteolin 7-O-glucoside (L7G) contents in the samples, a simple and fast HPLC method was developed and validated. Consequently, in water and hydroalcoholic extracts of O. europaea var. europaea leaves, oleuropein contents were found to be 15.89% (w/w) and 15.84% (w/w), while L7G contents were 0.75% and 1.23%, respectively. For the reference materials, oleuropein in O. europaea L. var. sylvestris leaves was found to be 12.77% (w/w, in water extract) and 12.36%(w/w, in hydroalcoholic extract), while the concentration of L7G was 0.51% (w/w) and 0.83% (w/w) in water and hydroalcoholic extracts, respectively. Qualitative analysis of the commercial products revealed that fraud was detected in three of eight olive leaf herbal tea bag brands and two of ten olive leaf food supplements. These samples were found either devoid of oleuropein or they had different HPTLC fingerprint profiles than the reference samples.

Keywords

• Olea europaea
• oleuropein
• ; luteolin 7-O-glucoside
• high-performance thin-layer chromatography (HPTLC)
• high-performance liquid chromatography (HPLC)
• quality control

References

1. [1] Salem M Ben, Affes H, Ksouda K, Sahnoun Z, Zeghal KM, Hammami S. Pharmacological activities of Olea europaea leaves. J Food Process Preserv. 2015; 39(6): 3128–3136. [CrossRef]
2. [2] Hashmi MA, Khan A, Hanif M, Farooq U, Perveen S. Traditional uses, phytochemistry, and pharmacology of Olea europaea (olive). Evidence-Based Complement Altern Med. 2015; 2015: 541591. [CrossRef]
3. [3] Esmaeili-Mahani S, Rezaeezadeh-Roukerd M, Esmaeilpour K, Abbasnejad M, Rasoulian B, Sheibani V, Kaeidi A, Hajializadeh Z. Olive (Olea europaea L.) leaf extract elicits antinociceptive activity, potentiates morphine analgesia and suppresses morphine hyperalgesia in rats. J Ethnopharmacol. 2010; 132(1): 200–205. [CrossRef]
4. [4] Yaltırık F, Olea L. In: Davis PH. (Ed). Flora of Turkey and the East Aegean Islands Vol. 6. Edinburgh University Press, Edinburgh 1978, pp.155-156.
5. [5] Eidi A, Eidi M, Darzi R. Antidiabetic effect of Olea europaea L. in normal and diabetic rats. Phytother Res. 2009; 23(3): 347–350. [CrossRef]
6. [6] Allouche Y, Warleta F, Campos M, Sánchez-Quesada C, Uceda M, Beltrán G, Gaforio JJ. Antioxidant, antiproliferative, and pro-apoptotic capacities of pentacyclic triterpenes found in the skin of olives on MCF-7 human breast cancer cells and their effects on DNA damage. J Agric Food Chem. 2011; 59(1): 121–130. [CrossRef]
7. [7] Fares R, Bazzi S, Baydoun SE, Abdel-Massih RM. The antioxidant and anti-proliferative activity of the Lebanese Olea europaea extract. Plant Foods Hum Nutr. 2011; 66(1): 58–63. [CrossRef]
8. [8] Pereira AP, Ferreira ICFR, Marcelino F, Valentão P, Andrade PB, Seabra R, Estevinho L, Bento A, Pereira JA. Phenolic compounds and antimicrobial activity of olive (Olea europaea L. Cv. Cobrançosa) leaves. Molecules. 2007; 12(5): 1153– 1162. [CrossRef]

9. [9] Lee O-H, Lee B-Y. Antioxidant and antimicrobial activities of individual and combined phenolics in Olea europaea leaf extract. Bioresour Technol. 2010; 101(10): 3751–3754. [CrossRef]
10. [10] Susalit E, Agus N, Effendi I, Tjandrawinata RR, Nofiarny D, Perrinjaquet-Moccetti T, Verbruggen M. Olive (Olea europaea) leaf extract effective in patients with stage-1 hypertension: Comparison with captopril. Phytomedicine. 2011; 18(4): 251–258. [CrossRef]
11. [11] Ikeda Y, Murakami A, Ohigashi H. Ursolic acid: An anti- and pro-inflammatory triterpenoid. Mol Nutr Food Res. 2008; 52(1): 26–42. [CrossRef]
12. [12] Dekanski D, Janićijević-Hudomal S, Tadić V, Marković G, Arsić I, Mitrović DM. Phytochemical analysis and gastroprotective activity of an olive leaf extract. J Serbian Chem Soc. 2009; 74(4): 367–377. [CrossRef]
13. [13] Koca U, Süntar I, Akkol EK, Yılmazer D, Alper M. Wound repair potential of Olea europaea L. leaf extracts revealed by in vivo experimental models and comparative evaluation of the extracts’ antioxidant activity. J Med Food. 2010; 14(1–2): 140–146. [CrossRef]
14. [14] Kaeidi A, Esmaeili-Mahani S, Sheibani V, Abbasnejad M, Rasoulian B, Hajializadeh Z, Afrazi S. Olive (Olea europaea L.) leaf extract attenuates early diabetic neuropathic pain through prevention of high glucose-induced apoptosis: In vitro and in vivo studies. J Ethnopharmacol. 2011; 136(1): 188–196. [CrossRef]
15. [15] Hassen I, Casabianca H, Hosni K. Biological activities of the natural antioxidant oleuropein: Exceeding the expectation - A mini-review. J Funct Foods. 2015; 18: 926–940. [CrossRef]
16. [16] Boka V-I, Argyropoulou A, Gikas E, Angelis A, Aligiannis N, Skaltsounis AL. Employment of High-Performance Thin-Layer Chromatography for the quantification of oleuropein in olive leaves and the selection of a suitable solvent system for its isolation with Centrifugal Partition Chromatography. Planta Med. 2015; 81(17): 1628–1635. [CrossRef]
17. [17] Gamlı ÖF. The health effects of oleuropein, one of the major phenolic compounds of olives, Olea europaea L. Ital J Food Sci. 2016; 28: 178–190. [CrossRef]
18. [18] European Pharmacopoeia (Ph. Eur.), Seventh ed., Council of Europe, Strasbourg, France, 2010.
19. [19] Benavente-García O, Castillo J, Lorente J, Ortuño A, Del Rio JA. Antioxidant activity of phenolics extracted from Olea europaea L. leaves. Food Chem. 2000; 68(4): 457–462. [CrossRef]
20. [20] Aziz N, Kim M-Y, Cho JY. Anti-inflammatory effects of luteolin: A review of in vitro, in vivo, and in silico studies. J Ethnopharmacol. 2018; 225: 342–358. [CrossRef]
21. [21] Qiusheng Z, Xiling S, Xubo, Gang L, Meng S, Changhai W. Protective effects of luteolin-7-glucoside against liver injury caused by carbon tetrachloride in rats. Pharmazie. 2004; 59(4): 286–289.
22. [22] Chanda S. Importance of pharmacognostic study of medicinal plants: An overview. J Pharmacogn Phytochem. 2014; 2(5): 69–73.
23. [23] ICH Harmonised Tripartite Guideline Validation of Analytical Procedures: Text and Methodology Q2 (R1). https://www.ich.org/fileadmin/Public_Web_Site/ICH_Products/Guidelines/Quality/Q2_R1/Step4/Q2_R1__G uideline.pdf (accessed on 8 August 2019)
24. [24] Özcan MM, Matthäus B. A review : Benefit and bioactive properties of olive (Olea europaea L.) leaves. Eur Food Res Technol. 2017; 243(1): 89–99. [CrossRef]
25. [25] Tutour BL, Guedon D. Antioxidative activities of Olea europaea leaves and related phenolic compounds. Phytochemistry. 1992; 31(4): 1173–1178. [CrossRef]
26. [26] Savournin C, Baghdikian B, Elias R, Dargouth-Kesraoui F, Boukef K, Balansard G. Rapid High-performance liquid chromatography analysis for the quantitative determination of oleuropein in Olea europaea leaves. J. Agric. Food Chem. 2001; 49: 618–621. [CrossRef]
27. [27] Lee-Huang S, Zhang L, Lin Huang P, Chang Y-T, Huang PL. Anti-HIV activity of olive leaf extract (OLE) and modulation of host cell gene expression by HIV-1 infection and OLE treatment. Biochem Biophys Res Commun. 2003; 307(4): 1029–1037. [CrossRef]
28. [28] Altınyay Ç, Altun ML. HPLC analysis of oleuropein in Olea europaea L. J Fac Pharm Ankara Univ. 2006; 35(1): 1–11.
29. [29] Al-Rimawi F. Development and validation of a simple reversed-phase HPLC-UV method for determination of oleuropein in olive leaves. J Food Drug Anal. 2014; 22: 285–289. [CrossRef]
30. [30] International Association for the Advancement of High Performance Thin Layer Chromatography. https://www.hptlc-association.org/methods/methods.cfm (accessed on 8 August 2019)