Table 2.

The biological activities of alkaloids. Numerous biological activities of alkaloids present in plants, their mechanism of action, and IC50 values are listed.

Alkaloid	Biological Activities	Mechanism of Action	IC50 Range	References
Paclitaxel	Antineoplastic and antimicrotubule	Suppresses microtubule dynamics by binding to β-tubulin subunits of microtubule and thereby inhibiting spindle function.	0.00126–12.3 µM	[123]
Vincristine	Antileukemic, antilymphoma, antineuroblastoma, and antisarcoma	Inhibits mitosis at the metaphase stage by interacting with tubulin; interferes with amino acids, cyclic AMP, glutathione metabolism, and calmodulin-dependent Ca2+-transport ATPase activity.	0.00126–1.01e + 3 µM	[123]
Camptothecin	Antitopoisomerase and anti-HIV	Causes DNA damage by binding to topoisomerase I and the DNA complex forming a ternary complex, stabilizing it, and preventing DNA re-ligation resulting in apoptosis.	0.00214–62.3 µM	[21]
Rohitukine	Anti-inflammatory, anti-fertility, anti-implantation, anti-cancer, and immuno-modulatory	Triggers apoptosis in lung cancer cells.	0.3–7.3 μM	[28]
Strychnine	Neurotoxic, pesticidal, and rodenticidal	Acts as an antagonist of glycine (an inhibitory neurotransmitter) and acetylcholine receptors, thereby preventing inhibitory signals and activating motor neurons in the spinal cord, resulting into spastic muscle contraction.	64–92 nM	[124]
Ephedrine	Promotes short-term weight loss, decreases motion sickness, possesses a cardiac stimulant, hyperglycaemic, hypertensive, bronchodilator	Indirectly stimulates the adrenergic receptor system by increasing the activity of norepinephrine at the postsynaptic α and β receptors. Acts as a CNS stimulant, due to its ability to cross the blood-brain barrier.	124 μM	[125]
Colchicine	Anti-gout, anti-inflammation, and treats familial Mediterranean fever	Inhibits mitosis by inhibiting microtubule polymerization; inhibits proinflammatory mechanisms and increases anti-inflammatory mediators; inhibits neutrophil motility and activity, interferes with superoxide formation, and thereby inhibits or prevents gout inflammation.	3–300 nM	[35]
Vasicine	Bronchodilator, mucolytic, antitussive, antibacterial, cytotoxic, abortifacient, and uterotonic	Acts as an acetylcholinesterase inhibitor and a butyrylcholinesterase inhibitor.	125 μM	[126,127]
Reserpine	Anti-hypertensive and anti-psychotic	Interferes with the sequestering of neurotransmitters into storage vesicles located in the presynaptic neuron by inhibiting their ATP/Mg2+ pump, causing a reduction in catecholamines, thereby causing antihypertensive effects.	1.7–2.8 μM	[128]
Ajmalicin	Anti-hypertensive	Acts as α1-adrenergic receptor antagonist and shows hypotensive effects.	3.5–5.44 μM	[11]
Tetrandrine	Anti-inflammatory, immunologic, anti-allergenic, and anti-tumour; used for treating Ebola virus infection in mice	Acts as a calcium-channel blocker, inhibits the degranulation of mast cells.	11.3 μM	[129]
Morphine	Analgesic and CNS stimulant	Acts as agonists for mu and kappa opioid receptors, on the ventral tegmental area of the brain; agonist of the delta-opioid receptor in the nucleus accumbens and activates the morphine reward pathway.	1–8.8 mM	[37]
Codeine	Analgesic, antidiarrheal, and antitussive	Acts as agonist for mu opioid receptors involved in the transmission of pain throughout the body and central nervous system.	60 μM	[130]
Papaverine	Vasodilatory and antispasmodic	Shows direct vasodilating action on cerebral blood vessels, increases cerebral blood flow and decreases cerebral vascular resistance.	2–37 μM	[6]
Berberine	Antimicrobial, antitumor, anti-hyperglycemic, antimalarial, and anti-inflammation; Alzheimer’s disease treatment	Lowers cholesterol through LDL-receptor-mediated liver LDL cholesterol clearance, promotes LDL-receptor expression through the proprotein convertase subtilisin/kexin type 9 (PCSK9)-LDL-receptor pathway.	0.1–25 µM	[131]
Scopolamine	Depressant action on sympathetic nervous system; possesses mydriatic, spasmolytic, and local anesthetic effects; treats motion sickness, postoperative nausea, and vomiting	Acts as a non-selective competitive inhibitor of M1-M5 mAChRs (G-protein-coupled muscarinic acetylcholine receptors), shows anticholinergic effect, and alters signalling through CNS associated with vomiting.	928 µM	[72]
Piperine	Presents hemo-preventive, anti-carcinogenic, antioxidant, anti-inflammatory, anticarcinogenic, stimulatory, hepatoprotective, antihyperlipidemia, anti-asthmatic activities; gastro-intestinal stimulant, and appetite stimulant	Affects the plasma concentrations of P-glycoprotein in the (P-gp)-mediated transport of drugs and metabolizes enzyme CYP3A4 substrates in humans; lowers endogenous UDP-glucuronic acid contents and inhibits transferase activity, thereby modifying the rate of glucuronidation.	1–34 μM	[132]
Lupinine	Insecticidal	Reversible inhibitor of acetylcholinesterases; possesses a binding affinity for muscarinic and nicotinic acetylcholine receptors.	712 μM	[133]
Swainsonine	Chemotherapeutic	Acts as a golgi α-mannosidase II inhibitor	34 nM	[134]
Skimmianine	Analgesic, antispastic, sedative, and anti-inflammatory	Suppresses TNF-α and IL-6 gene transcription, inhibits the production of NO, prostaglandin E2, and superoxide anions.	8.6 μg/mL	[20]
Theobromine	Antitumor, bronchorelaxater, and antitussive	Acts as antagonist to adenosine-receptors within the plasma membrane of virtually every cell, which further promotes neurotransmitter release.	2500 µM	[135]
Caffeine	Autonomous nervous system stimulant, anti-inflammation; improves cognitive performance	Inhibits the activity of nucleotide phosphodiesterase enzymes, regulates calcium handling in cells, and participates in adenosine receptor antagonism, stimulating inotropic effects in the heart.	500–1000 μM	[136]
Nicotine	Antiherbivore, insecticide, teratogenic, addictive, stimulant, and anxiolytic effects; treatment of nicotine dependence	Acts as an agonist/antagonist of certain nicotinic acetylcholine receptors, binding with receptors leading to depolarization, activating voltage-gated calcium channels.	0.5–20 nM	[137,138]
Veratridine	Inhibitor of sodium channel inactivation and neurotoxic	Depolarizes cells by affecting sodium channels, can activate Nav 1.8 along with additional Nav channels; enhances protein tyrosine phosphorylation; can turn the membrane potential to a more positive one and can also modify the effect of progesterone on (a2+)i and sperm membrane potential.	27–84 µM	[139]
Aconitine	Analgesic, blood coagulant, anti-inflammatory, cardiotoxic, and neurotoxic	Interacts with voltage-dependent sodium-ion channels, binds to the channel at the neurotoxin binding site 2 on the α-subunit, suppressing the conformational change in the sodium-ion channel from an active state to an inactive state.	10–20 µM	[140]
Hygrine	Sedative, hypnotic laxative, and diuretics	Not known.	Not reported	[31]
Boldine	Antioxidant, antipyretic, anti-inflammation, hepatoprotectant, cytoprotectant, and neuroprotectant	Acts as an α-adrenergic antagonist in vascular tissues; it can cross the blood-brain barrier exhibiting neuroprotective effects.	8.5 µM	[141]
Atropine	Anticholinergic, antispasmodic, and antimuscarinic	Binds and inhibits muscarinic acetylcholine receptors, producing anticholinergic effects.	2–55 µM	[32]
Capsaicin	Anti-obesity, antifungal action, and chemical irritant; treating peripheral neuropathy, psoriasis, and non-allergic rhinitis	Induces a topical hypersensitivity reaction on the skin by carrying out the “defunctionalization” of nociceptor fibers. Pain mechanism is due to temporary loss of membrane potential, inability to transport neurotrophic factors, and the reversible retraction of epidermal and dermal nerve fiber terminals.	50 μM	[142]
α-Solanine	Antiallergic, anti-inflammation, antipyretic, and anti-carcinogen; treating gastrointestinal and neurological disorders	Inhibits cholinesterase activity, disrupts cell membranes; opens the potassium channels of the mitochondria increasing their membrane potential, followed by the transport of Ca2+ from mitochondria into the cytoplasm leading to the an increased concentration of Ca2+ in the cytoplasm triggering cell damage and apoptosis.	32.18 μM	[143]
α-Tomatine	Anti-leukemia, fungicide, antimicrobial, and insecticide	Causes the disruption of cellular membranes and the inhibition of acetylcholinesterase; stimulates the immune system by participation in a sequence of respiratory burst destroying bacteria.	7–10 μM	[144]
Jatrorrhizine	Antibacterial and antifungal	Blocks α-1 and α-2 adrenoreceptors and monoamine oxidase A and B.	4–62 μM	[98]
Palmatine	Antimicrobial, hypoglycemic, antiarrhythmic, and antioxidant	Intercalates with nucleic acids; induces apoptosis; inhibits proliferation.	0.07–22 µM	[145]
Quinine	Antimalaria, mild antipyretic, and analgesic	Interferes with a parasite’s ability to break down and digest hemoglobin, leading to starvation in parasites.	13.4 µM	[146]
Cytisine	Teratogenic	Partial agonist of α4-β2 nicotinic acetylcholine receptors; causes a reduction in the effects of nicotine on dopamine release in the mesolimbic system when given alone, while simultaneously attenuates nicotine withdrawal symptoms accompanying cessation attempts.	27.3 nM	[147]