**4. Concluding remarks**

**3.14. Meliaceae –** *Azadirachta indica* **A. Juss.**

174 Herbal Medicine

Hindu ceremonies, festivals, and commemorations.

balms, creams as well as toothpastes and nail polishes [169].

among others, azadirachtin and nimbinin [167, 171].

**3.15. Oxalidaceae –** *Averrhoa bilimbi* **L.**

activity [175].

The neem tree *A. indica* is originally from the Asian subcontinent and is now grown in various tropical and semi-tropical regions. The bitter-tasting shoots and flowers are incorporated into various dishes, while preparations from leaves, bark, and fruits are consumed during many

*A. indica* leaves and seeds contain potent antiparasitic, insecticidal, and antimicrobial compounds such as the limonoids azadirachtin and nimbinin [167]. For this reason, dried neem leaves are placed in cupboards and storage facilities for grains to prevent damage from insects and burned to keep away mosquitoes, while the seed oil is used as a key ingredient of nonsynthetic ecofriendly pesticides in agriculture, acting as an antifeedant, repellent, and egglaying deterrent for insects [168]. The seed cake that remains after oil extraction is used as a fertilizer, enriching the soil with organic matter, and at the same time reducing nitrogen loss by inhibiting nitrification and averting damage to crops by termites and nematodes [168]. Neem oil is also a valuable ingredient of a large variety of cosmetics such as soaps, shampoos,

Parts of *A. indica* have been used for centuries in traditional and alternative medicinal systems in India and Suriname against a wide variety of diseases ranging from microbial infections and malaria to diabetes mellitus and hypertension [45, 170]. Some of these applications are supported by the results from pharmacological studies and may be related to the actions of,

Indications for a potential antihypertensive effect of *A. indica* preparations were provided by the inhibitory effect of *A. indica* yogurt on ACE activity *in vitro* [172], and the blood pressurelowering effect of leaf extracts in (salt-induced) rat models [173, 174]. Studies with laboratory rabbits suggested that these effects might also be due to vasodilation mediated through a combination of Ca2+ channel blockade, NO-inhibitory mechanisms, and cardiac depressant

The bilimbi *A. bilimbi* (**Figure 8**) presumably originates from Indonesia. It has been introduced in several Southeast Asian countries, and has spread to Australia as well as the Caribbean, Central America, and South America. The fruits can be eaten raw with salt and spice, pickled to obtain sweet and sour side dishes, incorporated in certain dishes as a souring agent, made into jams, or squashed to obtain a cooling beverage. However, *A. bilimbi* fruits (as well as leaves) contain high levels of oxalate [176] which may cause tubular necrosis and acute kid-

Parts of *A. bilimbi* have been important sources of medicines since antiquity. Decoctions, infusions, powders, and pastes have been used in several traditional medicinal systems including those in Suriname for preventing and treating many diseases such as skin eruptions, cough, cold, syphilis, diarrhea, obesity, diabetes mellitus, microbial infections, and hypertension [46, 178]. Physicochemical and pharmacological studies supported some of these uses [179].

ney failure when the concentrated juice is drunk on a daily basis [177].

This chapter has addressed the plants that are used in Suriname for treating hypertension. About 60 of the approximately 800 medicinal plants in Suriname are used against this condition ([45–55]; **Table 1**), indicating both the high need of antihypertensive medications and the high demand for traditional plant-derived for treating this condition in the country. As mentioned above, the prevalence of hypertension and other cardiovascular diseases is relatively high in Suriname [32, 36, 37], while most Surinamese have a long tradition of using ethnopharmacological preparations for treating their diseases [21, 44].

However, an extensive evaluation of 15 plants that are commonly used against hypertension in Suriname indicates that there is little scientific evidence for clinical efficacy against this condition. As shown in **Table 2**, 3 of the 15 plants (*A. graveolens*, *C. nucifera*, and *C. sativus*) had undergone preclinical as well as clinical evaluation against hypertension and turned out positive in at least some of the clinical studies. However, the clinical studies merely comprised a handful, although those with 3-n-butylphthalide in *A. graveolens* were sufficiently encouraging to prepare larger scale clinical evaluations [90–92].

Nine other plants (*M. indica*, *A. muricata*, *C. papaya*, *T. indica*, *P. americana*, *G. barbadense*, *H. sabdariffa*, *A. indica*, and *A. bilimbi*) have only been tested in preclinical models of hypertension (**Table 2**), relatively few of which involved animal studies. And three of the plants (*R. tuberosa*, *D. adscendens*, and *H. courbaril*) have never been assessed for potential antihypertensive effects, not even in preclinical models (**Table 2**). On the bright side, with the exception of *H. courbaril*, there were in all cases suggestions about the mechanisms that may be involved in the antihypertensive effects (**Table 2**). Then again, the chemical substances responsible for these effects were only provided for 6 plants (*M. indica*, *A. muricata*, *A. graveolens*, *C. nucifera*, *H. sabdariffa*, and *A. indica*; **Table 2**).

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Plant-Based Ethnopharmacological Remedies for Hypertension in Suriname

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These data clearly indicate that the scientific evidence accumulated so far to support the use of plant-based traditional medicines in Suriname against hypertension is scant. This raises not only the possibility that patients treat their disease with substances that may be ineffective, but also that they may run the risk of unknown or unforeseen adverse effects. For these reasons, it is necessary to subject these plants to comprehensive phytochemical and pharmacological investigations, elaborate preclinical evaluations, and well-designed and well-executed clinical studies to definitely establish their roles in the treatment of hypertension. Obviously, these enterprises will require considerable efforts from both academia and industry, but may eventually payoff when considering the importance of ancient wisdom and folk medicine to drug discovery and development programs [183].
