Caper (Capparis spinosa L.): An Updated Review on Its Phytochemistry, Nutritional Value, Traditional Uses, and Therapeutic Potential

Abstract

Caper (Capparis spinosa L.) is a perennial shrub of the family Capparaceae, endemic to circum-Mediterranean countries. Caper carries a renowned nutritional value, especially in terms of vitamins and antioxidants related to the occurrence of flavonoids, alkaloids, and glucosinolates as main secondary metabolites. Caper extracts have also shown to display antibacterial, antifungal, analgesic, antitumor, hepatoprotective, antioxidant, anti-inflammatory, and neuroprotective effects which correlate the uses of the plant in folk medicine against both metabolic and infectious diseases. The present review aims to provide exhaustive phytochemistry and pharmacological properties survey on Caper constituents. Attention has also been given to the nutritional values and traditional uses of main organs to pinpoint research gaps for future investigations on the plant.

Keywords: antidiabetic; caper bush; capparaceae; flavonoids; flinders rose; glucosinolates; hepatoprotective; indoles.

FIGURE 1

(A) Visualization of topic areas of Caper research using overlay visualization. (B) Term map generated from all keyword’s fields on Caper and representing the different research themes that defined different clusters. Cluster 1 is colored in red on the term map and represents the botanical and geographical distribution of the plant. This cluster represents research publications on the relationship between the genetic variation and distribution of the plant in different areas. Cluster 2 is colored in green and represents the antioxidant activity of Caper and its correlation with compounds, especially quercetin and kaempferol. Cluster 3 is colored in blue on the map. This cluster represents the ethnopharmacological properties of aper in traditional medicine. The different uses depend on the local zones of distribution. Cluster 4 is colored in yellow. The cluster is broadly classified as publications linked with the in vivo activity of the plant related to liver disease and diabetes, with the mechanism of the plant on these human diseases.

FIGURE 2

Nucleosides and nucleic acids from Caper. 1 = Uracil, 2 = Uridine, 3 = Inosine, 4 = Adenosine, 6 = Hypoxanthine.

FIGURE 3

Alkaloids isolated from roots and fruits of Caper. R = β-D-glucopyranosyl, 6 = (-)-Stachydrine, 7 = 4-Hydroxy-1H-indole-3-carboxaldehyde, 8 = Cappariloside A, 9 = Cappariloside B, 10 = 1-(2-Hydroxy-6-methoxy-1H-indol-3-yl)ethanone, 11 = 2,3-Dihydro-7-hydroxy-2-oxo-1H-indole-3-acetic acid, 12 = Indole-3-carbaldehyde, 13 = Indole-3-carboxylic acid, 14 = Flazin, 15 = 1-(6-Methyl-2-pyrazinyl)-1,2,3,4-butanetetrol, 16 = Cadabicine, 17 = Isocodonocarpine, 18 = Capparisine, 19 = Codonocarpine, 20 = Capparispine, 21 = Capparispine 26-O-β-D-glucose, 22 = Cadabicine 26-O-β-D-glucose.

FIGURE 4

(A) Sulfur-containing compounds from Caper. (B) Furan and pyrrole analogues reported in Caper. R = β-D-glucopyranosyl, 23 = Glucobrassicin, 24 = Neoglucobrassicin, 25 = 4-Methoxyglucobrassicin, 26 = 4-Hydroxyglucobrassicin, 27 = 6-Methoxy-2-(methylthio)-1H-indole-3-carboxaldehyde, 28 = (3S)-(-)-6-Methoxy-2'-(methylthio)spiro[3H-indole-3,5′(4′H)-thiazol]-2(1H)-one, 29 = Glucocapparin, 30 = 5,5'-[Oxybis(methylene)]bis[2-furancarboxaldehyde], 31 = 5-(Hydroxymethyl)furfural, 32 = 4-Hydroxy-5-methyl-3-furancarboxylic acid, 33 = 5-(Methoxymethyl)-1H-pyrrole-2-carbaldehyde, 34 = 3,4,5-trihydroxypentanoic acid γ-lactone, 35 = Capparisine B, 36 = 2-(5-hydroxymethyl-2-formylpyrrol-1-yl) propionic acid lactone, 37 = Capparisine A, 38 = N-(30-maleimidy1)-5-hydroxymethyl-2-pyrrole formaldehyde, 39 = Capparisine C.

FIGURE 5

Flavonoids isolated in Caper organs. R = β-D-glucopyranosyl, R¹ = rutinosyl, R² = β-D-glucorhamnoside, R³ = 6‘-O-rutinosyl-O-β-D-glucoside, 40 = Kampferol, 41 = Apigenin, 42 = Rutin, 43 = kaempferol 3-O-rutinoside, 44 = Oroxylin A, 45 = Wogonin, 46 = Sakuranetin, 47 = Astragalin, 48 = quercetin 3-O-[6‴-α-L-rhamnosyl-6″-β-D-glucosyl]-β-D-glucoside, 49 = Isorhamnetin, 50 = Quercetin 7-O-β-D-glucorhamnoside, 51 = Ginkgetin, 52 = Isoginkgetin.

FIGURE 6

Terpenes and other compounds from Caper. R = β-D-glucopyranosyl, R² = 6‘-stearyl-β-D-glucopyranosyl, 53 = (6S,7E)-6,9-Dihydroxymegastigma-4,7-dien-3-one, 54 = 4-Hydroxy-4-(3-hydroxy-1-buten-1-yl)-3,5,5-trimethyl-2-cyclohexen-1-one, 55 = (4S)-4-[(1E,3S)-3-(ß-D-Glucopyranosyloxy)-1-buten-1-yl]-4-hydroxy-3-(hydroxymeth…, 56 = Corchoionoside C, 57 = (2R)-2-[(1E,3R)-3-(ß-D-Glucopyranosyloxy)-1-buten-1-yl]-2-hydroxy-1,3-dimethyl-5…, 58 = (1R,5R,8S)-8-[(1E,3S)-3-(ß-D-Glucopyranosyloxy)-1-buten-1-yl]-8-hydroxy-1,5-dime…, 59 = (1R,5R,8S)-8-Hydroxy-8-[(1E,3S)-3-hydroxy-1-buten-1-yl]-1,5-dimethyl-6-oxabicycl…, 60 = Phaseic acid, 61 = Methyl α-D-fructofuranoside, 62 = 1-prenylglucopyranoside, 63 = β-Sitosterol, 64 = Daucosterol, 65 = Daucosterol 6'-O-stearate, 66 = alpha-tocopherol, 67 = (2R,4aR,8aR)-3,4,4a,8a-Tetrahydro-4a-hydroxy-2,6,7,8a-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-chromene-5,8-dione, 68 = myo-Inositol, 69 = (R)-2,4-Dimethoxy-2-methyl-6H-pyran-3-one, 70 = Isopsoralen, 71 = Sporalen.

FIGURE 7

Selected biological activities of Caper.

FIGURE 8

Distribution of MW (A); F Csp3 (B); number of RBs (C); Log P (D); TPSA (E); and Log S (F) accordingly to the class of compounds. Comparison between the values of F Csp3 carbons and MW (G); log P and MW (H); MW and TPSA (I); MW and log S (J); log P and log S (K); TPSA and log S (L). Heatmap of the compliance with rules of drug-likeness for the compound’s classes (M). A (Alkaloids), G (Glucosinolates), F&P (Furans), F (Flavonoids), and T&M (terpenoids and miscellaneous).