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The main compounds of interest to brewers in hops are their bitter acids and oils contained in the yellow-colored lupulin glands. There are at least 250 significant aroma and flavor compounds found in hop acids and oils. Alpha acids account for roughly 2-17% of dried hops by mass, beta acids account for roughly 2-10%, and oils account for roughly 0.5-3%, though the exact percentages will vary depending on factors such as the hop varietal, growing region, harvest time, and growth conditions for the year. The rest of the weight of hops is contained in the leafy matter called Bract and is made up of 40-50% cellulose and lignin, 15% protein, 8-12% water (after drying), 8% minerals, 3-6% polyphenols and tannins, 1-5% lipids and fatty acids, 2% monosaccharides, and 2% pectin <ref name="Algazzali_2014">[http://www.asbcnet.org/publications/journal/vol/2016/Pages/ASBCJ-2016-1130-01.aspx The Bitterness Intensity of Oxidized Hop Acids: Humulinones and Hulupones. Victor Alexander Algazzali for the degree of Master of Science in Food Science and Technology presented on August 8, 2014.]</ref><ref>[https://www.researchgate.net/publication/297161591_HUMULUS_LUPULUS_L_HOPS_-_A_VALUABLE_SOURCE_OF_COMPOUNDS_WITH_BIOACTIVE_EFFECTS_FOR_FUTURE_THERAPIES HUMULUS LUPULUS L. (HOPS) – A VALUABLE SOURCE OF COMPOUNDS WITH BIOACTIVE EFFECTS FOR FUTURE THERAPIES. Jana Olšovská et al. 2016.]</ref>.