With the rise of global health awareness by embracing a healthy lifestyle and natural product consumption, the search for natural antioxidant sources has invited more research performed especially in fruits as a whole product or in its components, especially the ones that are usually discarded/not the mainly consumed component. Pyrus communis and Pyrus pyrifolia are two of the most popular species of pear fruits consumed in the world, and while there exist several studies about the antioxidant potential of its flesh, specific studies about the antioxidant properties of their peels are still lacking. To achieve an understanding of antioxidant properties of peel extract of P. communis and P. pyrifolia, several tests have been performed in controlled laboratory conditions to gauge phenolic and flavonoid contents through three different extraction measurements. This research has shown that peel extracts of both P. communis and P. pyrifolia contain natural antioxidants that are beneficial for health, with P. communis extracted with methanol having a higher concentration of antioxidant contents compared to P. pyrifolia.

In food research, phenolic compounds withantioxidant activity holds an important position. This is related to the factthat phenolic compounds play a beneficial effect on preventing and/or treatingvarious diseases, such as cancer, diabetes, cardiovascular andneurodegenerative diseases, among others (Cory et al., 2018; Panche et al., 2016; Pandey & Rizvi, 2009). Phenolic is an important bioactive and possessstrong antioxidant activity, and fruits and vegetables usually are the primarysources of Phenolic compound (Tungmunnithumet al., 2018). It is widely believed that the ingestion offresh fruits and vegetables is related to the reduction of cardiovascular andcancer diseases (Aghajanpour et al., 2017).

Pear (Pyrusspp) have been known to contain a number of phytochemical compounds withimportant bioactive properties like phenolics and flavonoids, which areessential for their health benefits (Öztürk et al., 2015). Those health benefits of polyphenol consumptionderive from their antioxidant and anti-inflammatory properties (Borges et al.,2010). Other pro-healthproperties that are attributed to pears are related to the content oftriterpenoids, due to their antioxidative, anti-inflammatory, and anticancerproperties (Reiland & Slavin, 2015).

During recent years, some researchers have beenfocused on analyses and comparison of the nutritional components contained inthe edible part of pear fruit such as total sugars, vitamins, minerals, and soon (Slavin & Lloyd, 2012; Kahle et al., 2005; Tanriöven & Ekşi, 2005). A part from some common reported compounds suchas arbutin, chlorogenic acid, catechin, quercetin, kaempferol, varioushydroxycinnamoylmalic acids, and their ethyl esters, hydroxycinnamoyl malates,procyanidins, and triterpenes compound has also been found in the peel of pear(Lee et al.,2011a; Lee et al., 2011b; Ma et al., 2012).

Pears is one of the fruits imported into Indonesiawhich is often found in supermarkets or traditional markets. Pears which arewidely circulating in Indonesia are Pyruscommunis or green pears/European pears and Pyrus pyrifolia or yellow pears/Asian pears (Novera et al.,2015). Pears are usuallyconsumed along with the peels, although consuming the fruit while discardingthe peels are also common, because the peels are often viewed as non-beneficial(Sagar et al.,2018). With this fact,understanding the potentials and bioactive compounds of pear peel as a sideproduct of the fruit is very important (Li et al., 2014).

Based on our study in this matter, we found thatthe information on the composition and constituents of pear peel are limited.Therefore, we propose that it is important for food products research to have asystematic study on pear peel, especially on the phenolic and flavonoidcompounds. The aim of this research is to identify the total phenolic andantioxidant contents, and performing qualitative determination of phytochemicalcontents for the two pear varieties.

The main materialused in the study are P. communis and P. pyrifolia.Both samples of pears were obtained from Caringin’s Traditional Market,Bandung, West java that imported from Australia and China, respectively. Othermaterials used were methanol, ethyl acetate, n-hexane, ethanol, ascorbic acid, gallic acid, quercetin,Folin-Ciocalteu’s phenol reagent (Sigma), aquadest, chloroform, toluene,acetone, 25% ammonia 2 N, 10% hydrochloric acid, Dragendorff reagent, Mayerreagent, Mg powder, amyl alcohol, sodium hydroxide, gelatin, Fe (III) chloride1%, and anhydrous acetic acid. The tools used are sifters, cups, oven,desiccators, maceration chamber, erlenmeyer flasks, vacuum rotary evaporator,analytical scales, and micropipette. Spectrophotometric measurements wereperformed on ultraviolet (UV)-1600 spectrophotometer (Shimadzu).

Both pear peelsamples that have been collected and cleaned are dried by drying the cabinet at40-50°C until smooth and dry.

Pear peels wereextracted by maceration in 200 ml of n-hexane,ethyl acetate and methanol at room temperature for 24 hours. Residues andextracts are separated by filtering using filter paper. The residue obtainedwas re-extracted twice with a fresh portion of the extraction solvent. Extractsobtained from the three extraction processes were combined and excess solventswere concentrated using a vacuum rotary evaporator at 50°C. Semisolid extracts obtained quantitatively were transferred toextraction solvents and stored at 10°C until used forfurther experiments.

Phytochemicalcompounds were carried out for all extracts with the following methods:

Steroids and terpenoids

As much as 2 ml ofextract was added to 2 ml of acetic anhydride and the concentrated H2SO4.The formation of blue with green rings indicates the presence of terpenoids andthe brown rings indicate the presence of steroids (Ayoola et al., 2008).

Alkaloids

Extracts weredissolved individually in dilute hydrochloric acid and filtered. Filtrates weretreated with Dragendroff’s reagent (solution of Potassium Bismuth Iodide). TheFormation of red precipitate indicates the presence of alkaloids (Altemimi et al.,2017).

Saponins

As much as 0.5 gof extract was shaken with 2 ml of water. If foam produced persists for tenminutes it indicates the presence of saponins (Altemimi et al., 2017).

Tannins

To the extract, 1%gelatin solution containing sodium chloride was added. The Formation of whiteprecipitate indicates the presence of tannins (Altemimi et al., 2017).

Phenolics

Extracts weretreated with 3-4 drops of ferric chloride solution. The Formation ofbluish-black color indicates the presence of phenols (Altemimi et al., 2017).

Flavonoids

Extracts weretreated with a few drops of sodium hydroxide solution. Formation of intenseyellow colour, which becomes colourless on the addition of dilute acid,indicates the presence of flavonoids (Altemimi et al., 2017).

Total polyphenolwas determined by Folin-Ciocalteu method (Aryal et al., 2019). A dilute extract of each plant extract (0.5 mlof 1 : 10 g/ml) or gallic acid (standard phenolic compound) was mixed withFolin-Ciocalteu reagent (5 ml, 1 : 10 diluted with distilled water) and aqueousNa2CO3 (4 ml, 1 M). The mixtures were allowed to standfor 15 minutes and the total phenols were determined by colorimetry at 765 nm.The standard curve was prepared using 0, 50, 100, 150, 200, and 250 mg/Lsolutions of gallic acid in methanol : water (50 : 50, v/v). Total phenolvalues are expressed in terms of gallic acid equivalent (mg/g of dry mass),which is a common reference compound.

Aluminum chloridecolorimetric method was used for flavonoids determination (da Silva et al.,2015). Each plant extracts(0.5 ml of 1 : 10 g/ml) in methanol were separately mixed with 1.5 ml ofmethanol; 0.1 ml of 10% aluminum chloride; 0.1 ml of 1 M potassium acetate; and2.8 ml of distilled water. It remained at room temperature for 30 minutes. Theabsorbance of the reaction mixture was measured at 415 nm with UV-Visspectrophotometer. The calibration curve was prepared by preparing quercetinsolutions at concentrations 12.5 to 100 g/ml in methanol.

Results are given as the mean of three independentdeterminations ± standard deviation using SPSS version 19.0. The data werestatistically analyzed by ANOVA and t-tests.The level of statistical significance was set at p <0.05.

Phytochemical screening of the two varieties ofpeel pears shows that both have the same content, namely phenolic, flavonoids,tannins, saponins, and alkaloids as shown in Table I. All of these phytochemicals are important elements of herbal medicineand are directly related to various health-promoting activities such asanticancer, antifungal, anti-inflammatory, antihyperglycemic, immunomodulatory,and wound healing properties (Forni et al., 2019). However, flavonoidcontent in P. communis is greaterthan P. pyrifolia.

Flavonoids havebeen found to possess antitumoral, antiallergic, and anti-inflammatoryactivities (Panche et al.,2016). Phenolic content is thegreatest content found in both P. communisand P. pyrifolia. In particular, manyphenolic compounds have been identified in pear fruits such as arbutin,chlorogenic acid, hyroxycinnamoyl malates, catechins, and procyanidins (Sun et al., 2019).

Table I. Qualitativephytochemical screening in P. communisand P. pyrifolia peels

Note: (++) highly presence; (+) presence; (-) absence

In P. communis peels, totalextraction yields from n-hexane,ethyl acetate, and methanol were 11.35%; 17.95%; and 30.85%, respectively asshown in Table II. In P. pyrifoliapeels, total extraction yields were 13.50%; 18.75%; and 37.50%, respectively aspresented in Table III. In both P. communisand P. pyrifolia peels, the highestyields were observed in methanol extract and higher in the P. pyrifolia peel extracts. The extractable compounds from variousplant materials are strongly dependant on the nature of extractable solvents.Methanol is one of the polar solvents used for active component extractionwhich can attract many compounds such as anthocyanins, terpenoids, saponins,tannins, xanthoxyllines, quassinoids, lactones, flavones, phenones, andpolyphenols (Mujeeb et al.,2014).

Table II. Total extraction yieldsof P. communis peels

Table III. Total extraction yields of P. pyrifolia peels

The antioxidant activityof plant phenolics is due to the reactivity of phenol moieties (hydroxyl groupon the aromatic ring) which have the ability to scavenge free radicals viahydrogen donation or electron donation or electron donation. Total phenolics weredetermined by Folin-Ciocalteu reagent method. In this method, phenols from ablue-colored phosphomolybdic-phosphotungstic complex in the presence of analkaline solution (Saeed et al., 2012).

The total phenolic contents in P. communispeels were 7.20 ± 0.03 mg/g; 33.35 ± 0.57 mg/g; and 68.86 ± 0.78 mg from n-hexane, ethyl acetate, and methanolextracts, respectively. Statistically significant the lowest yields wereobserved in n-hexane extracts as compared to ethyl acetate and methanol extractwhile the latter two have the same significantly different too. In the case of P. pyrifolia peels, the contents from n-hexane, ethyl acetate, and methanolextracts were 8.45 ± 0.11 mg/g; 31.22 ± 0.68 mg/g; and 63.50 ± 0.41 mg/g,respectively. Statistical significance was similar to P. communis peels as presented in Figure 1. Methanol extract have the highest content which werehigher in the P. communis peels (68.8mg GAE/g) than in the P. pyrifolia peels(63.5 mg GAE/g). This result is in agreement with Singh & Rajini (2004) which reportedthat the maximum antioxidant yield was obtained with methanol compared toacetone and water.

Figure 1. Total phenolic contents of P. communis and P. pyrifoliapeels by solvents

The total flavonoid contents in P.communis peels from n-hexane,ethyl acetate, and methanol were 11.72 ± 0.72 mg/g; 49.75 ± 1.72 mg/g; and62.84 ± 0.77 mg/g, respectively. In the case of P. pyrifolia peels, the observed contents were 10.91 ± 0.14 mg/g;40.69 ± 0.84 mg/g; and 50.9 ± 1.45 mg/g, respectively. Analytic results showthat n-hexane, ethyl acetate, andmethanol extracts on P. communis peelswere significantly different from P. pyrifoliapeels. From the result, the highest content was observed in methanol extractsthere are 62.84 mg QE/g in P. communispeel and 50.9 mg QE/g in P. pyrifoliapeel as presented in Figure 2.Methanol is an effective solvent for polyphenols, and then it is commonly usedin the laboratory and in industrial extraction process (Zhang et al., 2018).

Figure 2. Total flavonoid contents of P. communis and P. pyrifoliapeels by solvents

It can be seen that the total contents ofpolyphenol and flavonoid have the same trends. Total phenolic content and totalflavonoid contents for both the varieties of pear peels showed that methanolextracts are the highest values and P. communis peels contained more phenolic and flavonoid contents than P. pyrifolia peels.

From this study, it is concludedthat two varieties of pear peel show the presence of phytochemicals, there arephenolics, flavonoids, tannins, alkaloids, and saponins. Methanol extracts isthe highest amount of total phenol and total flavonoids contents both P. communis and P. pyrifolia peels which P. communis peels exhibited more amounts of phenolic and flavonoids than P. pyrifolia peels. The presence of thesebioactive compounds in pears varieties establishes themselves as the sources ofnatural therapeutic agents that can act as potent free radical scavengers.

This project was supported byMinistry of Research and Technology Republic of Indonesia and Universitas MuhammadiyahBandung in 2019.

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