Chapter 109 Opuntia Species (Prickly Pear)
Opuntia spp. (family: Cactaceae)
Common names: prickly pear, nopal
There are about 260 species of Opuntia.1 These cacti are shrubs, and their flat, pear-shaped pads are stems or branches, not leaves, as many suppose. Some prickly pear varieties form thickets many feet tall and many feet across. Prickly pear’s flowers range from yellow to orange and red to rose. Their fruits come in shades of yellow through red to purple. Most species have glochids, sometimes referred to as tiny spines, although they are actually leaf hairs with tiny barbs.2 The stems, fruits, and flowers are all used as medicines.
Comparisons of the constituents of the many prickly pear species are sparse, and there is no indication that any particular species is a better medicinal plant. The pad is high in mucilage, consisting of carbohydrate-containing polymers.3 The pads also contain a mixture of saturated and unsaturated long-chain aliphatic esters; daidzein; genistein; β-sitosterol; and vanillic, ferulic, myristic, palmitic, and stearic acids.3–6 Prickly pear fruits are high in carbohydrates and contain the pigments indicaxanthin and betanin.7 The flowers contain flavonoids such as quercetin and isorhamnetin-3 glucosides in varying amounts.8
History and Folk Use
Prickly pear has a long history of medicinal use. The Aztecs used prickly pear root with Geranium spp. (cranesbill) as a febrifuge, to alleviate hernias, and to soothe irritated livers.9 The fruit and seeds were used to prevent diarrhea. Indigenous peoples along the Yaqui River used the fluid from roasted prickly pear pads to relieve pain.10 In New Mexico, prickly pear pads were used as poultices for painful, inflamed skin conditions, for swollen glands in the neck, and for congested, purplish breasts in lactating women. The pads were also used as emollients for tumors, warts, and calluses. The Tarahumara used the pads for the pain of bites and burns, and the Paipai used them to heal festering wounds. The Yaqui and the Hispanics in New Mexico soak diced pads in water and drink the liquid for thirst and diabetes; they also use the roasted pad to treat diabetic infections. Prickly pear was brought from the Americas to Africa and Europe, and its medicinal uses followed.11
Today, the Moors apply the heated pads to swellings on the body, the South African Bantu use prickly pear for a variety of tumors, and Zimbabweans use prickly pear internally as a treatment for pain in gouty arthritis.12,13 In the Canary Islands, prickly pear fruits are used topically for a variety of inflamed wounds and internally for gastrointestinal and bronchial problems. In the Mediterranean region, prickly pear pads are used to treat gastric ulcers, and in Sicilian folk medicine, a flower infusion is used for its diuretic and relaxant action on the kidneys.14
Prickly pear fruits and pads had significant analgesic effects in mice.15 Prickly pear fruit injected intraperitoneally (400 mg/kg) had an analgesic effect comparable to that of aspirin (70 mg/kg) in vivo.
Prickly pear significantly reduced edema in rat paws and showed an antiinflammatory effect in a mouse model of chronic inflammation.16 The active constituent was identified as β-sitosterol. Another study showed that prickly pear (O. dillenii) fruit extract injected intraperitoneally had antiinflammatory action.17 Pretreatment with prickly pear significantly reduced edema dose-dependently, and its maximal effect was similar to that of indomethacin.
After reports that a woman stopped frequent recurrent outbreaks of herpes genitalis by taking 2 g prickly pear a day, studies investigated the plant’s antiviral effects.18 In hamster kidney cells, prickly pear specifically reduced herpes simplex virus type 2 (HSV-2) replication at 3.5 mg/mL, and completely inhibited replication at 15 mg/mL. Prickly pear also inhibited other herpes viruses (pseudorabies virus, bovine mammillitis virus, equine herpes virus type 1, as well as the more cell-associated human herpes virus, cytomegalovirus, and varicella zoster virus).
Prickly pear inhibited replication by HSV-2 in infected human cervix tissue and inhibited RNA virus replication.18 Testing included a laboratory strain of influenza A virus, an isolate of respiratory syncytial virus, and strains of encephalomyocarditis (EMC) virus, and HIV-1. The only virus that prickly pear failed to inhibit was the picornavirus EMC. The researchers found prickly pear to be a promising antiviral agent because it combines a breadth of in vitro reactivity with a high index of clinical safety. However, prickly pear pads combined with fresh Capsicum frutescens (cayenne) fruit and fresh Citrus limon (lemon) did not protect chickens from Newcastle virus.19
When administered by mouth, dried prickly pear pad (O. ficus indica) significantly inhibited hydrochloride-induced, aspirin-induced, and ethanol-induced gastric lesions in rats.20,21 Prickly pear did not affect gastric juice secretion, acid output, or stomach pH in the rats. Extracts of O. ficus indica showed significant wound healing activity in rats.22
Diuretic and Other Renal Effects
Fruit and flower infusions of O. ficus indica significantly increased diuresis in rats, and the fruit infusion had an antiuric effect.23 Prickly pear pads (20 mg/100 g body weight daily for 5 weeks) significantly decreased uric acid levels and increased water intake while only slightly raising urine output in rats.24 Although the rise in urine flow was slight, the investigators suggested that it could account for the greater excretion of uric acid. O. megacantha pads (20 mg/kg daily for 5 weeks) significantly increased urinary sodium output in diabetic rats and normal rats compared with controls.25 Prickly pear did not alter plasma aldosterone concentrations. In earlier studies, prickly pear extract administered orally (20 mg/100 g body weight) increased creatinine clearance in diabetic rats and raised plasma creatinine and urea levels in all rats.24,26
Animal studies showed prickly pear pad had a hypoglycemic effect in streptozotocin-induced diabetes in rats and rabbits, although one study showed no effect if the rabbits’ pancreatic β-cells were completely obliterated.26–29 In one study, prickly pear’s hypoglycemic effect was comparable to that of tolbutamide.27 Prickly pear and insulin equivalently reduced, but did not normalize, glucose and insulin levels in diabetic rats. Prickly pear combined with insulin had a synergistic effect. Diabetic rats given the combination rapidly achieved normal glucose levels, and at 7 weeks became hypoglycemic. At that point, prickly pear alone was sufficient to maintain normal glucose levels.28