Stories: The Longevity Spinach

Here in Malaysia and parts of Asia, there lives a herb with such exaggerated medicinal benefits, it’s called the longevity spinach or sambung-nyawa, in Bahasa. From lowering blood pressure, to curing diabetes, to busting cholesterol, reducing inflammation, whatever, it would make you a better person. So famous is this herb, it’s even introduced and cultivated in the United States and beyond. I’m not sure about you, but don’t you think when something sounds too good to be true, it probably is? Moreover, this isn’t even a spinach to begin with!

Gynura procumbens (Asteraceae)

The longevity spinach (Gynura procumbens) is herbaceous plant belonging to the daisy family (Asteraceae). Just so you know, edible spinach belongs to the unrelated  Amaranthaceae family. The Latin name procumbens (cumbere) means ‘lay down’, alluding to the growth habit of this species, which is often a droopy creeper. While there are indeed preliminary scientific studies to suggest that Gynura procumbens exhibit anti-diabetic, anti-inflammation, and anti-cholesterol activity, those were not human studies, and they were performed on lab rats, or isolated cells in a petri dish.  To the best of my knowledge, there are currently no human trials of Gynura procumbens in treating any diseases. This is usually the case for many traditional herbs, and they surely demand more research, especially those that produce promising results in animal models such as Gynura procumbens. However, the genus Gynura, which comprises some 40 species, is well known to produce a group of toxins called pyrrolizidine alkaloids (prominent in Asteraceae plants). In fact, several species of Gynura such as G. japonica and G. segetum are prominent traditional Chinese medicines (土三七), and their uses have caused serious poisoning and death to humans. Other species of Gynura, which are commonly consumed including G. bicolor and G. procumbens are shown to contain similarly toxic pyrrolizidine alkaloids in varying quantities. While no one is known to have poisoned or died from the longevity spinach, Gynura procumbens is certainly of high concern considering its widespread use as a medicinal herb. In fact, pyrrolizidine alkaloid poisoning is chronic and insidious. It may take many months if not years for symptoms to occur, and by which time it’s often too late. That’s why I am sharing some relatively recent scientific articles about the subject matter.

Reference: Zhu, L.; Zhang, C. yuan; Li, D. ping; Chen, H. biao; Ma, J.; Gao, H.; Ye, Y.; Wang, J. yao; Fu, P. P.; Lin, G. Acta Pharmacol. Sin. 2020, 1–11.

Here in this review article, scientists investigated about 2000 cases of confirmed pyrrolizidine alkaloid toxicosis in China due to consumption of Gynura japonica as a medicinal herb. The poisoning causes a specific form of liver disease called hepatic sinusoidal obstruction syndrome, which in its late stage carries a mortality rate of more than 80%. I have explained this condition in my science article on the toxicology of pyrrolizidine alkaloids (cf. hepatic veno-occlusive disease). China also appears to have a high rate of drug induced liver damage, about 24 per 100,000 population, which is far greater than the estimates from Western countries. It is thus speculated that traditional Chinese medicines containing pyrrolizidine alkaloids were largely responsible. In fact, many of the poisoning cases were due to self-medication by lay people, who confused Gynura japonica with benign traditional Chinese herbs of similarly sounding names. What a deadly mistake! Looking back, I wonder how many people are self-medicating themselves with Gynura procumbens? I certainly hope it is not nearly as toxic as Gynura japonica. In fact, scientists have even developed a method to definitively diagnose pyrrolizidine alkaloid poisoning by quantifying the amount of dihydropyrrolizine-protein adduct in a patient’s blood (find the mechanism here). With time, the true extent and prevalence of pyrrolidizine alkaloid toxicity due to medicinal herbs would be known. Thus far, the case fatality rate of liver damage induced by Gynura japonica and Gynura segetum ranged anywhere from 10% to 50% within five years. Remember that pyrrolizidine alkaloid induced liver damage is chronic, somewhat cumulative, irreversible, and most suffering.  

 

Reference: Ji, Y. Bin; Wang, Y. S.; Fu, T. T.; Ma, S. Q.; Qi, Y. D.; Si, J. Y.; Sun, D. A.; Liao, Y. H. Int. J. Environ. Anal. Chem. 2019, 99 , 1090–1102.

There is no doubt about the lethal potential of Gynura japonica and Gynura segetum, but what about our local longevity spinach? Here is a study that I have long awaited. Scientists from China have finally quantified the levels of pyrrolizidine alkaloids in of Gynura procumbens using a method called LCMS-MS. They have extracted fresh Gynura procumbens leaves, as well as medicinal herb products containing this species, to selectively concentrate alkaloidal contents. Then, they compared this enriched alkaloid extract with reference standards of known pyrrolizidine alkaloids, including retronecine, senecionine etc, many of which are known to cause serious human toxicity. The method LCMS-MS basically separates a crude extract into individual components by liquid chromatography (LC). The separated components are then turned into ions by a strong electric current. These ions can then be accelerated under an electric field to have their mass (molecular weight) determined by a process called mass spectrometry (MS). Essentially, a more heavy ion will be harder to accelerate compared to a lighter ion. In the second (tandem) MS process, we can even filter out a particular ion of interest for further analysis. Thus, the amount and identity of a substance like pyrrolizidine alkaloid can be confirmed by comparison with a known reference standard. Different compounds are unlikely to produce a similar mass ion and fragmentation pattern. LCMS-MS is currently the gold standard in chemistry including forensic toxicology to detect and quantity a given drug or toxin from biological specimens. So what did the scientists found in Gynura procumbens? Eleven pyrrolidizine alkaloids including some highly toxic ones, in concentrations ranging from 16 – 848 micrograms per kilogram dried plant material. That’s honestly not too much, about the mass of a grain of rice! But here’s the catch, the daily allowable intake of pyrrolizidine alkaloid in any food is just 0.35 micrograms per day per 50 kg adult human. It is that toxic! While it is now confirmed that Gynura procumbens contains toxic pyrrolizidine alkaloids in substantial quantity, what constitutes a safe dose and a safe period of consumption remained unknown. Animal studies have shown that Gynura procumbens is safe up to 6 grams plant/ kilogram / day for 13 weeks, but again, we are not lab rats. Therefore, the authors warned that Gynura procumbens may pose a health risk to people, and I concur with their opinion. 

I honestly do not know if the longevity spinach does what it’s supposed to do, but pyrrolizidine alkaloids and several species of Gynura can certainly contribute to the opposite of longevity. Medicinal herbs are a promising resource for pharmaceutical research, and so are they to the people who seek alternatives to modern medicine. Speaking as a phytochemist, I would be glad to see the eventual isolation of active principles, or perhaps quantification of standardised extracts from medicinal herbs to ensure their efficacy and safety. For now however, I sincerely urge caution to those that are/plan to consume the longevity spinach over long-term, you wouldn't want to have chronic liver failure. Remember that plants do not grow to serve us as food or medicine, some of them produce powerful toxins to protect themselves. Make sure you really know what you're eating before you convince yourself that natural 'medicines' are all good!