*2.1. Chemicals*

The following reagents were obtained from Sigma Co. (St. Louis, MO, USA): catechin, kaempferol, isorhamnetin, naringenin, quercetin, butylated hydroxytoluene (BHT), Folin–Ciocalteu's phenol reagent, copper sulfate, ethylenediaminetetraacetic acid (EDTA), β-glucuronidase type H-2 (containing sulfatase from *Helix pomatia*), glutathione reductase (type III), nicotinamide adenine dinucleotide phosphate (NADP), sodium 1-octanesulfonate monohydrate, reduced glutathione, oxidized glutathione, sodium azide, sodium chloride, sodium phosphate monobasic, sodium phosphate dibasic, 1,1,3,3-tetraethoxypropane, 2',3',4'-trihydroxyacetophenone, Tris buffer, magnesium chloride, triphenylphosine, and α-tocopherol. Diisopropylethylamine (DIPEA), O-bis (trimethylsilyl) trifluoroacetamide (BSTFA), and pentafluorobenzyl bromide (PFBBr) were purchased from Thermo (Boston, MA, USA). Deuterated prostaglandin (PG) F2α (internal standard), PGF2β, and 8-iso-PGF2α were purchased from Cayman (Ann Arbor, MI, USA). All organic solvents, glacial acetic acid, and potassium bromide were purchased from Fisher Co. (Fair Lawn, NJ, USA).

#### *2.2. Preparation of ASP*

Almond skin powder was generously provided by the Almond Board of California. Polyphenols in 150 and 300 g almond skin powder were extracted sequentially twice using a ratio of 0.5:10 (w/v) with acidified ethanol solution (white vinegar/H2O/200 proof ethanol at 1/19/80) over 16 h at 4 ◦C. The extraction solution was selected with consideration of the extract for human use. The resulting solution was centrifuged at 1000× *g* for 15 min at 4 ◦C, followed by ethanol removal using a Buchi R215 Rotary Evaporator equipped with a Vacuum Controller V-850 (Flawil, Switzerland). The total phenol content in the resulting aqueous syrup was determined by Folin–Ciocalteu's assay [27] and expressed as gallic acid equivalents (GAE). The GAE content produced from 150 and 300 g almond skin powder was 225 and 450 mg, respectively. ASP were stored overnight at 4 ◦C before administration to the volunteers the following morning.
