Morinda citrifolia

Long before noni juice reached the health-food shelf, the mengkudu tree's
leaves were the working part of the plant. McClatchey's 2002 historical
review documents that traditional Polynesian indications centred on
leaves, roots and bark applied topically — and that the fruit-juice
framing is a modern commercial invention [1]. The heated-leaf poultice —
the leaf warmed over a flame and pressed to boils, bites and swellings —
is recorded across the region's practice [2]. This monograph is about the
leaf; the fruit literature is out of its scope and, as the Safety section
notes, must not be conflated with it.

The leaf's chemistry is distinct from the fruit's: flavonoids (kaempferol,
rutin), iridoids of the asperuloside series with aucubin, and coumarins
including scopoletin, surveyed in recent reviews [2, 3], with early
leaf-specific glycoside work by Sang and colleagues [4]. What heating over
a flame — the defining step of the traditional preparation — does to those
constituents has never been characterised.

The leaf's laboratory record includes one directly relevant animal study:
Nayak and colleagues (2009) gave ethanolic leaf extract in rat excision
and dead-space wound models and reported 71% wound-area reduction by day
11 against 57% in controls [5]. That is wound closure in rodents — not
insect bites, not histamine response, not humans.

Nothing in the verified literature tests the poultice practice itself: no
human study of heated mengkudu leaf on bites or minor skin complaints
exists. The traditional record is strong, the leaf's safety data are
unusually good for this library (below), and the clinical question is
completely open. Grade C.

The leaf is one of the better-characterised botanicals in this library
for safety, because European novel-food regulation demanded it: the EFSA
panel assessed dried and roasted mengkudu leaves for infusions and set an
intake ceiling of 18.4 mg/kg body weight per day [6], and West and
colleagues (2007) reported negative acute, subacute and subchronic
toxicity and anaphylaxis testing for leaf extracts [7]. The widely cited
hepatotoxicity case reports concern noni fruit juice, not the leaf [8],
and a head-to-head chronic study in mice found toxicity signals with
high-dose fruit extract while leaf extracts showed none [9]. A bite that
is spreading, blistering or systemically unwell needs clinical care, not
a poultice.

A systematic review from the Herbal Medicine Research Centre at Malaysia's
Institute for Medical Research assessed both efficacy and safety across the
noni literature [10] — a useful regulatory-adjacent reference precisely
because it does not overstate. Separate Malaysian work on the leaf reports
performance and vascular effects in animal models without the toxicity
signals associated with high-dose fruit extract [11, 12].